LCS Technical Reports (1974 - 2003)

The AEGIS Processor Architecture for Tamper-Evident and Tamper-Resistant Processing

2023-04-01T03:34:49Z

The AEGIS Processor Architecture for Tamper-Evident and Tamper-Resistant Processing Suh, G. Edward; Clarke, Dwaine; Gassend, Blaise; van Dijk, Marten; Devadas, Srinivas We describe the architecture for a single-chip AEGIS processor which can be used to build computing systems secure against both physical and software attacks. Our architecture assumes that all components external to the processor, such as memory, are untrusted. We show two different implementations. In the first case, the core functionality of the operating system is trusted and implemented in a security kernel. We also describe a variant implementation assuming an untrusted operating system. AEGIS provides users with tamper-evident, authenticated environments in which any physical or software tampering by an adversary is guaranteed to be detected, and private and authenticated tamper-resistant environments where additionally the adversary is unable to obtain any information about software or data by tampering with, or otherwise observing, system operation. AEGIS enables many applications, such as commercial grid computing, secure mobile agents, software licensing, and digital rights management. We also present a new encryption/decryption method that successfully hides a significant portion of encryption/decryption latency, in comparison to a conventional direct encryption scheme. Efficient memory encryption and integrity verification enable the implementation of a secure computing system with the only trusted component being a single-chip AEGIS CPU. Preliminary simulation results indicate that the overhead of security mechanisms in AEGIS is reasonable.

The AEGIS Processor Architecture for Tamper-Evident and Tamper-Resistant Processing

2023-03-30T16:31:15Z

The AEGIS Processor Architecture for Tamper-Evident and Tamper-Resistant Processing Suh, G. Edward; Clarke, Dwaine; Gassend, Blaise; van Dijk, Marten; Devadas, Srinivas We describe the architecture of the AEGIS processor which can be used to build computing systems secure against both physical and software attacks. AEGIS assumes that the operating system and all components external to it, such as memory, are untrusted. AEGIS provides tamper-evident, authenticated environments in which any physical or software tampering by the adversary is guaranteed to be detected, and private and authenticated, tamper-resistant environments where additionally the adversary is unable to obtain any information about software or data by tampering with, or otherwise observing, system operation. AEGIS enables many applications, such as commercial grid computing, software licensing, and digital rights management. We present a new encryption/decryption method that successfully hides a significant portion of encryption/decryption latency, in comparison to a conventional direct encryption scheme. Efficient memory encryption and integrity verification enable the implementation of a secure computing system with the only trusted component being a single-chip AEGIS CPU. Detailed simulation results indicate that the performance overhead of security mechanisms in AEGIS is reasonable.

AEGIS: Architecture for Tamper-Evident and Tamper-Resistant Processing

2023-03-30T16:39:35Z

AEGIS: Architecture for Tamper-Evident and Tamper-Resistant Processing Suh, G. Edward; Clarke, Dwaine; Gassend, Blaise; van Dijk, Marten; Devadas, Srinivas We describe the architecture for a single-chip AEGIS processor which can be used to build computing systems secure against both physical and software attacks. Our architecture assumes that all components external to the processor, such as memory, are untrusted. We show two different implementations. In the first case, the core functionality of the operating system is trusted and implemented in a security kernel. We also describe a variant implementation assuming an untrusted operating system. AEGIS provides users with tamper-evident, authenticated environments in which any physical or software tampering by an adversary is guaranteed to be detected, and private and authenticated tamper-resistant environments where additionally the adversary is unable to obtain any information about software or data by tampering with, or otherwise observing, system operation. AEGIS enables many applications, such as commercial grid computing, secure mobile agents, software licensing, and digital rights management. Preliminary simulation results indicate that the overhead of security mechanisms in AEGIS is reasonable.

Hybrid I/O Automata*

2023-04-01T03:54:13Z

Hybrid I/O Automata* Lynch, Nancy A.; Segala, Roberto; Vaandrager, Frits Hybrid systems are systems that exhibit a combination of discrete and continuous behavior. Typical hybrid systems include computer components, which operate in discrete program steps, and real-world components, whose behavior over time intervals evolves according to physical constraints. Important examples of hybrid systems include automated transportation systems, robotics systems, process control systems, systems of embedded devices, and mobile computing systems. Such systems can be very complex, and very difficult to describe and analyze. This paper presents the Hybrid Input/Output Automaton (HIOA) modeling framework, a basic mathematical framework to support description and analysis of hybrid systems. An important feature of this model is its support for decomposing hybrid system descriptions. In particular, the framework includes a notion of external behavior for a hybrid I/O automaton, which captures its discrete and continuous interactions with its environment. The framework also defines what it means for one HIOA to implement another, based on an inclusion relationship between their external behavior sets, and defines a notion of simulation, which provides a sufficient condition for demonstrating implementation relationships. The framework also includes a composition operation for HIOAs, which respects external behavior, and a notion of receptiveness, which implies that an HIOA does not block the passage of time. The framework is intended to support analysis methods from both computer science and control theory. This work is a simplification of an earlier version of the HIOA model [49, 50]. The main simplification in the new model is a clearer separation between the mechanisms used to model discrete and continuous interaction between components. In particular, the new model removes the dual use of external variables for discrete and continuous interaction.

Hybrid I/O Automata*

2025-06-19T03:10:21Z

Bandwidth Management in Wireless Sensor Networks

2023-03-30T03:39:27Z

Bandwidth Management in Wireless Sensor Networks Hull, Bret; Jamieson, Kyle; Balakrishnan, Hari Wireless sensor networks are often used in monitoring and control applications, where software running on generalpurpose computers ÔøΩpullÔøΩ information from remote sensors and ÔøΩpushÔøΩ actuations into the network. The sensors themselves form a multihop wireless network communicatingwith one or more sensor access points (SAPs) that interface between application software and the sensor network. This paper addresses the problem of managing wireless network bandwidth and improving network capacity in a sensor network deployed as a shared infrastructure, concurrently used by different applications. Our bandwidth management architecture incorporates three ideas: first, we develop a simple rule system that allows applications and the network administrator to specify how traffic generated by sensors should be treated by the sensor network. Each rule is a function that maps a sensor data type and generated value to a transmission rate and a traffic class. Second, we show how using multiple SAPs and SAP selection method that considers packet loss probabilities, path load, and path lengths improves the capacity of the network and the performance of individual sensor streams. Third, we show that hopby- hop flow control, rather than end-to-end congestion control, is a better way to cope with the nature of sensor network traffic and avoids unnecessary packet losses that waste valuable wireless network bandwidth. Our experimental results from a 40-node indoor wireless sensor testbed show that these three techniques are simple to implement and allow scarce network bandwidth to be used efficiently.

Computer-Enforced Immutability for the Java Language

2023-03-30T03:48:11Z

Computer-Enforced Immutability for the Java Language Birka, Adrian This thesis presents the design, implementation, and evaluation of an extension to the Java language, ConstJava, that is capable of expressing immutability constraints and verifying them at compile time. The specific constraint expressed in ConstJava is that the transitive state of the object to which a given reference refers cannot be modified using that reference. In addition to the ability to specify and enforce this basic constraint, ConstJava includes several other features, such as mutable fields, immutable classes, templates, and the const cast operator, that make ConstJava a more useful language. The thesis evaluates the utility of ConstJava via experiments involving writing ConstJava code and converting Java code to ConstJava code. The evaluation of ConstJava shows that the language provides tangible benefits in early detection and correction of bugs that would otherwise be difficult to catch. There are also costs associated with the use of ConstJava. These are minimized by ConstJavaÔøΩs backward compatibility with Java, and by the high degree of inter-operability of the two languages, which allows for a less painful transition from Java to ConstJava. This technical report is a revision of the authorÔøΩs MasterÔøΩs thesis, which was advised by Prof. Michael D. Ernst.

Compositionality for Probabilistic Automata

2023-03-30T03:18:33Z

Compositionality for Probabilistic Automata Lynch, Nancy A.; Segala, Roberto; Vaandrager, Frits We establish that on the dfomain of probabilistic automata, the trace distribution preorder coincides with the simulation preorder.

Subexponential Parameterized Algorithms on Graphs of Bounded Genus and H-minor-free Graphs

2023-03-30T03:24:07Z

Subexponential Parameterized Algorithms on Graphs of Bounded Genus and H-minor-free Graphs Demaine, Erik D.; Fomin, Fedor V.; Hajiaghayi, Mohammad Taghi; Thilikos, Dimitrios M. We introduce a new framework for designing fixed-parameter algorithms with subexponential running time---2^O(sqrt k) n^O(1). Our results apply to a broad family of graph problems, called bidimensional problems, which includes many domination and covering problems such as vertex cover, feedback vertex set, minimum maximal matching, dominating set, edge dominating set, clique-transversal set, and many others restricted to bounded genus graphs. Furthermore, it is fairly straightforward to prove that a problem is bidimensional. In particular, our framework includes as special cases all previously known problems to have such subexponential algorithms. Previously, these algorithms applied to planar graphs, single-crossing-minor-free graphs, and/or map graphs; we extend these results to apply to bounded-genus graphs as well. In a parallel development of combinatorial results, we establish an upper bound on the treewidth (or branchwidth) of a bounded-genus graph that excludes some planar graph H as a minor. This bound depends linearly on the size |V(H)| of the excluded graph H and the genus g(G) of the graph G, and applies and extends the graph-minors work of Robertson and Seymour. Building on these results, we develop subexponential fixed-parameter algorithms for dominating set, vertex cover, and set cover in any class of graphs excluding a fixed graph H as a minor. In particular, this general category of graphs includes planar graphs, bounded-genus graphs, single-crossing-minor-free graphs, and any class of graphs that is closed under taking minors. Specifically, the running time is 2^O(sqrt k) n^h, where h is a constant depending only on H, which is polynomial for k = O(log^2 n). We introduce a general approach for developing algorithms on H-minor-free graphs, based on structural results about H-minor-free graphs at the heart of Robertson and Seymour's graph-minors work. We believe this approach opens the way to further development on problems in H-minor-free graphs.

Fixed Parameter Algorithms for Minor-Closed Graphs (of Locally Bounded Treewidth)

2023-03-30T03:55:07Z

Fixed Parameter Algorithms for Minor-Closed Graphs (of Locally Bounded Treewidth) Demaine, Erik D.; Hajiaghayi, Mohammad Taghi Frick and Grohe showed that for each property phi that is definable in first-order logic, and for each class of minor-closed graphs of locally bounded treewidth, there is an O(n^(1+epsilon))-time algorithm deciding whether a given graph has property phi. In this paper, we extend this result for fixed-parameter algorithms and show that any minor-closed [contraction-closed] bidimensional parameter which can be computed in polynomial time on graphs of bounded treewidth is also fixed-parameter tractable on general minor-closed graphs [minor-closed class of graphs of locally bounded treewidth]. These parameters include many domination and covering parameters such as vertex cover, feedback vertex set, dominating set, and clique-transversal set. Our algorithm is very simple and its running time is explicit (in contrast to the work of Frick and Grohe). Along the way, we obtain interesting combinatorial bounds between the aforementioned parameters and the treewidth of the graphs.

Equivalence of Local Treewidth and Linear Local Treewidth and its Algorithmic Applications

2023-03-30T03:49:30Z

Equivalence of Local Treewidth and Linear Local Treewidth and its Algorithmic Applications Demaine, Erik D.; Hajiaghayi, Mohammad Taghi We solve an open problem posed by Eppstein in 1995 and re-enforced by Grohe concerning locally bounded treewidth in minor-closed families of graphs. A graph has bounded local treewidth if the subgraph induced by vertices within distance r of any vertex has treewidth bounded by a function of r (not n). Eppstein characterized minor-closed families of graphs with bounded local treewidth as precisely minor-closed families that minor-exclude an apex graph, where an apex graph has one vertex whose removal leaves a planar graph. In particular, Eppstein showed that all apex-minor-free graphs have bounded local treewidth, but his bound is doubly exponential in r, leaving open whether a tighter bound could be obtained. We improve this doubly exponential bound to a linear bound, which is optimal. In particular, any minor-closed graph family with bounded local treewidth has linear local treewidth. Our bound generalizes previously known linear bounds for special classes of graphs proved by several authors. As a consequence of our result, we obtain substantially faster polynomial-time approximation schemes for a broad class of problems in apex-minor-free graphs, improving the running time from 2^(2^(2^O(1/epsilon))) n^O(1) to 2^O(1/epsilon) n^O(1).

Snapshots in a Distributed Persistent Object Storage System

2023-03-30T03:37:17Z

Snapshots in a Distributed Persistent Object Storage System Moh, Chuang-Hue

Incremental Multiset Hash Functions and their Application to Memory Integrity Checking

2023-03-30T03:46:11Z

Incremental Multiset Hash Functions and their Application to Memory Integrity Checking Clarke, Dwaine; Devadas, Srinivas; van Dijk, Marten; Gassend, Blaise; Suh, G. Edward We introduce a new cryptographic tool: multiset hash functions. Unlike standard hash functions which take strings as input, multiset hash functions operate on multisets (or sets). They map multisets of arbitrary finite size to strings (hashes) of fixed length. They are incremental in that, when new members are added to the multiset, the hash can be updated in time proportional to the change. The functions may be multiset-collision resistant in that it is diÔøΩcult to find two multisets which produce the same hash, or just set-collision resistant in that it is diÔøΩcult to find a set and a multiset which produce the same hash. In particular, we introduce four multiset hash functions, each with its own advantages. MSet-XOR-Hash uses the XOR operation and is very eÔøΩcient; however, it uses a secret key and is only set-collision resistant. MSet-Add-Hash uses addition modulo a large integer and, thus, is slightly less eÔøΩcient than MSet-XOR-Hash; MSet-Add-Hash also uses a secret key but it is multiset-collision resistant. MSet-Mu-Hash uses finite field arithmetic and is not as eÔøΩcient as the other two hash functions; however, MSet-Mu-Hash is multiset-collision resistant, and unlike the other two hash functions, does not require a secret key. MSet-VAdd-Hash is more eÔøΩcient than MSet-Mu-Hash; it is also multiset-collision resistant, and does not use a secret key, but the hashes it produces are significantly longer than the hashes of the other functions. The proven security of MSet-XOR-Hash and MSet-Add-Hash is quantitative. We reduce the hardness of finding collisions to the hardness of breaking the underlying pseudorandom functions. The proven security of MSet-Mu-Hash is in the random oracle model and is based on the hardness of the discrete logarithm problem. The proven security of MSet-VAdd-Hash is also in the random oracle model and is based on the hardness of the worst-case shortest vector problem. We demonstrate how set-collision resistant multiset hash functions make an existing oÔøΩine memory integrity checker secure against active adversaries. We improve on this checker such that it can use smaller time stamps without increasing the frequency of checks. The improved checker uses multiset-collision resistant hash functions

Improving Application-level Network Services with Regions

2023-03-30T03:25:26Z

Improving Application-level Network Services with Regions Li, Ji The underlying premise of the Region Project is that the concept of a region should be a new architecture capability in networking. A region is an entity that encapsulates and implements scoping, grouping, subdividing, and crossing boundaries of sets of entities. It is a powerful tool for managing the increasingly complex demands on the Internet and its successors, and thus should be made into an explicit, first-class component of the network architecture. Autonomous Systems and peer-to-peer networks can be viewed as two simple forms of existing regions. In this work, we explore the utility of informing members in one region of the membership of those same entities in different regions. Specifically, we improve peer-to-peer networks with information derived from Autonomous Systems. This thesis makes three notable contributions. Firstly, we provide a general peer-to-peer simulation framework for different optimization schemes. Secondly, we achieve performance improvements in the lookup, caching and replication of peer-to-peer system. Finally, we enhance our overall understanding of regions through the simulation, as well as their utilities to improve system performance.

Sift: A MAC Protocol for Event-Driven Wireless Sensor Networks

2023-03-30T03:40:54Z

Sift: A MAC Protocol for Event-Driven Wireless Sensor Networks Jamieson, Kyle; Balakrishnan, Hari; Tay, Y.C. Nodes in sensor networks often encounter spatially-correlated contention, where multiple nodes in the same neighborhood all sense an event they need to transmit information about. Furthermore, in many sensor network applications, it is sufficient if a subset of the nodes that observe the same event report it. We show that traditional carrier-sense multiple access (CSMA) protocols like 802.11 do not handle the first constraint adequately, and do not take advantage of the second property, leading to degraded latency and throughput as the network scales in size. We present Sift, a medium access protocol for wireless sensor networks designed with the above observations in mind. Sift is a randomized CSMA protocol, but unlike previous protocols, does not use a time-varying contention window from which a node randomly picks a transmission slot. Rather, to reduce the latency for the delivery of event reports, Sift uses a fixed-size contention window and a carefully-chosen, non-uniform probability distribution of transmitting in each slot within the window. We show using simulations that Sift can offer up to a 7-fold latency reduction compared to 802.11 as the size of the sensor network scales up to 500 nodes. We then analytically prove bounds on the best latency achievable by a decentralized CSMA-based MAC protocol for sensor networks where one report of each event is enough, and show that Sift comes close to meeting this bound.

Anchor-free Distributed Localization in Sensor Networks

2023-03-30T03:38:37Z

Anchor-free Distributed Localization in Sensor Networks Priyantha, Nissanka B.; Balakrishnan, Hari; Demaine, Erik; Teller, Seth Many sensor network applications require that each node's sensor stream be annotated with its physical location in some common coordinate system. Manual measurement and configuration methods for obtaining location don't scale and are error-prone, and equipping sensors with GPS is often expensive and does not work in indoor and urban deployments. Sensor networks can therefore benefit from a self-configuring method where nodes cooperate with each other, estimate local distances to their neighbors, and converge to a consistent coordinate assignment. This paper describes a fully decentralized algorithm called AFL (Anchor-Free Localization) where nodes start from a random initial coordinate assignment and converge to a consistent solution using only local node interactions. The key idea in AFL is fold-freedom, where nodes first configure into a topology that resembles a scaled and unfolded version of the true configuration, and then run a force-based relaxation procedure. We show using extensive simulations under a variety of network sizes, node densities, and distance estimation errors that our algorithm is superior to previously proposed methods that incrementally compute the coordinate of nodes in the network, in terms of its ability to computer correct coordinates under a wider variety of conditions and its robuestness to measurement errors.

System Dependence Graph Construction for Aspect-Oriented Programs

2023-03-30T03:18:57Z

System Dependence Graph Construction for Aspect-Oriented Programs Zhao, Jianjun; Rinard, Martin We extend previous dependence-based representations called system dependence graphs (SDGs) to represent aspect-oriented programs and present an SDG construction algorithm. This algorithm first constructs a module dependence graph (MDG) for each piece of advice, introduction, and method in aspects and classes. It then uses existing techniques to connect the MDGs at call sites to form a partial SDG. Finally, it weaves the MDG for each piece of advice into the partial SDG for those methods whose behavior may be affected by the advice. The result is the complete SDG. Our SDGs capture the additional structure present in many aspect-oriented features such as join points, advice, introduction, aspects, and aspect inheritance, and various types of interactions between aspects and classes. They also correctly reflect the semantics of aspect-oriented concepts such as advice precedence, introduction scope, and aspect weaving. SDGs therefore provide a solid foundation for the further analysis of aspect-oriented programs.

RAMBO II: Rapidly Reconfigurable Atomic Memory for Dynamic Networks

2023-03-30T04:11:03Z

RAMBO II: Rapidly Reconfigurable Atomic Memory for Dynamic Networks Gilbert, Seth; Lynch, Nancy A.; Shvartsman, Alexander A. Future civilian rescue and military operations will depend on a complex system of communicating devices that can operate in highly dynamic environments. In order to present a consistent view of a complex world, these devices will need to maintain data objects with atomic (linearizable) read/write semantics.

Inference of Generic Types in Java

2023-03-30T03:34:32Z

Inference of Generic Types in Java Donovan, Alan; Ernst, Michael D. Future versions of Java will include support for parametric polymorphism, or generic classes. This will bring many benefits to Java programmers, not least because current Java practise makes heavy use of pseudo-generic classes. Such classes (for example, those in package java.util) have logically generic specifications and documentation, but the type system cannot prove their patterns of use to be safe. This work aims to solve the problem of automatic translation of Java source code into Generic Java (GJ) source code. We present two algorithms that together can be used to translate automatically a Java source program into a semantically-equivalent GJ program with generic types. The first algorithm infers a candidate generalisation for any class, based on the methods of that class in isolation. The second algorithm analyses the whole program; it determines a precise parametric type for every value in the program. Optionally, it also refines the generalisations produced by the first analysis as required by the patterns of use of those classes in client code.

Building Data Structures on Untrusted Peer-to-Peer Storage with Per-participant Logs

2023-03-30T04:20:55Z

Building Data Structures on Untrusted Peer-to-Peer Storage with Per-participant Logs Chen, Benjie; Gil, Thomer M.; Muthitacharoen, Athicha; Morris, Robert T. L* is a technique for building multi-user distributed data structures out of untrusted peer-to-peer distributed hash tables (DHTs). L* uses multiple logs, one log per participant, to store changes to the data structure. Each participant finds data by consulting all logs, but performs modifications by appending only to its own log. This dencentralized structure allows L* to maintain meta-data consistency without locking and to isolate users' changes from each other, an appropriate arrangement for unreliable users. Applications use L* to maintain consistent data structures. L* interleaves multiple logs deterministically so that decentralized clients can agree on the order of completed operations, even if those operations where issued concurrently. When the data structure is quiescent, L* guarantees that clients agree on the state of the data structure. L* optionally provides mutual exclusion for applications that need to ensure atomicity for multi-step operations. The Ivy file system, built on top of L*, demonstrates that L*'s consistency guarantees are useful and can be used and implemented efficiently.

Efficient Consistency Proofs on a Committed Database

2023-03-30T03:10:48Z

Efficient Consistency Proofs on a Committed Database Ostrovsky, Rafail; Rackoff, Charles; Smith, Adam A consistent query protocol allows a database owner to publish a very short string c which commits her to a particular database D with special consistency property (i.e., given c, every allowable query has unique and well-defined answer with respect to D.) Moreover, when a user makes a query, any server hosting the database can answer the query, and provide a very short proof P that the answer is well-defined, unique, and consistent with c (and hence with D). One potential application of consistent query protocols is for guaranteeing the consistency of many replicated copies of D---the owner can publish c, and users can verify the consistency of a query to some copy of D by making sure P is consistent with c. This strong guarantee holds even for owners who try to cheat, while creating c. The task of consistent query protocols was originally proposed for membership queries by Micali and Rabin, and subsequently and independently, by Kilian. In this setting a server can prove to a client whether or not a given key is present or not in a database, based only on a short public commitment c. We strengthen their results in several ways. For membership queries, we improve the communication complexity; more importantly, we provide protocols for more general types of queries and more general relational databases. For example, we consider databases in which entries have several keys and where we allow range queries (e.g. we allow a client to ask for all entries within a certain age range and a certain salary range). Towards this goal, we introduce query algorithms with certain inherent robustness properties---called data-robust algorithms---and show how this robustness can be achieved. In particular, we illustrate our general technique by constructing an efficient data-robust algorithm for proving consistency of orthogonal range queries (a particular case of a ``join''query). The server's proof convinces the client not only that all the matching entries provided are in D, but also that no others are present. Our guarantees hold even if the answer is the empty set. In the case of one-dimensional range queries we also show a new data-hiding technique---called explicit hashing---which allows us to a execute consistent query protocol P and at the same time protect the privacy of all other information in the database efficiently. In particular, we avoid the NP reductions required in a generic zero-knowledge proof.

REX: Secure, modular remote execution through file descriptor passing

2023-03-30T03:11:18Z

REX: Secure, modular remote execution through file descriptor passing Kaminsky, Michael; Peterson, Eric; Fu, Kevin; Mazières, David; Kaashoek, M. Frans The ubiquitous SSH package has demonstrated the importance of secure remote login and execution. This paper presents a new system, REX, designed to provide remote login and execution in the context of the SFS secure distributed file system. REX departs from traditional remote login design and is built around two main mechanisms---file descriptor passing and a user agent process. File descriptor passing allows REX to be split into several smaller pieces; privileged code can run as its own process to provide enhanced security guarantees. REX also emulates secure file descriptor passing over network connections, allowing users to build extensions to REX outside of the core REX software. REX uses and extends SFS's agent mechanism to provide a transparent distributed computing environment to users. The agent stores private keys, server nicknames, and other per-user configuration state; REX makes the SFS agent available to programs that it executes on remote machines. We have an implementation of REX and demonstrate that its flexibility does not come at the cost of performance. Initial REX connections are comparable to those of SSH in speed, while subsequent connections are much faster because REX exploits the SFS agent to cache connection state to avoid costly public-key operations.

The AEGIS Processor Architecture for Tamper-Evident and Private Tamper-Resistant Processing

2023-03-30T16:25:53Z

The AEGIS Processor Architecture for Tamper-Evident and Private Tamper-Resistant Processing Suh, G. Edward; Clarke, Dwaine; Gassend, Blaise; van Dijk, Marten; Devadas, Srinivas We describe the architecture of the AEGIS processor which can be used to build computing systems secure against both physical and software attacks. AEGIS assumes that the operating system and all components external to it, such as memory, are untrusted. AEGIS provides tamper-evident, authenticated environments in which any physical or software tampering by the adversary is guaranteed to be detected, and private and authenticated, tamper-resistant environments where additionally the adversary is unable to obtain any information about software or data by tampering with, or otherwise observing, system operation. AEGIS enables many applications, such as commercial grid computing, software licensing, and digital rights management. We present a new encryption/decryption method that successfully hides a significant portion of encryption/decryption latency, in comparison to a conventional direct encryption scheme. Efficient memory encryption and integrity verification enable the implementation of a secure computing system with the only trusted component being a single-chip AEGIS CPU. Detailed simulation results indicate that the performance overhead of security mechanisms in AEGIS is reasonable.

Efficient Web Browsing for Mobile Clients using HTTP Compression

2023-03-30T03:06:13Z

Efficient Web Browsing for Mobile Clients using HTTP Compression Krashinsky, Ronny Efficient web browsing on mobile computers presents a unique challenge. These machines are different from other classes of client computers since they have relatively low-bandwidth connections and they are battery-powered and therefore limited by their energy consumption. However, they tend to interact with the same servers for the delivery of web content. This project investigates optimizing the final critical link between a mobile client and a stationary base station by compressing HTTP request and response messages. Using a split proxy design, compression of individual request messages reduces bandwidth by 26% to 34% across a variety of benchmark traces, and applying compression to response messages yields savings of 59% to 82% of the compressible data. Higher compression rates are achieved by using streaming compression algorithms to compress the streams of request and response messages. In this case, the bandwidth for requests sees an order of magnitude improvement, and the response stream obtains additional savings of 7% to 25% on top of the savings achieved with per-response compression.

Physical Random Functions

2023-03-30T03:44:13Z

Physical Random Functions Gassend, Blaise In general, secure protocols assume that participants are able to maintain secret key information. In practice, this assumption is often incorrect as an increasing number of devices are vulnerable to physical attacks. Typical examples of vulnerable devices are smartcards and Automated Teller Machines. To address this issue, Physical Random Functions are introduced. These are Random Functions that are physically tied to a particular device. To show that Physical Random Functions solve the initial problem, it must be shown that they can be made, and that it is possible to use them to provide secret keys for higher level protocols. Experiments with Field Programmable Gate Arrays are used to evaluate the feasibility of Physical Random Functions in silicon.

On the Theory of Structural Subtyping

2023-03-30T03:40:03Z

On the Theory of Structural Subtyping Kuncak, Viktor; Rinard, Martin We show that the first-order theory of structural subtyping of non-recursive types is decidable. Let Sigma be a language consisting of function symbols (representing type constructors) and C a decidable structure in the relational language L containing a binary relation <. C represents primitive types; < represents a subtype ordering. We introduce the notion of Sigma-term-power of C, which generalizes the structure arising in structural subtyping. The domain of the Sigma-term-power of C is the set of Sigma-terms over the set of elements of C. We show that the decidability of the first-order theory of C implies the decidability of the first-order theory of the Sigma-term-power of C. This result implies the decidability of the first-order theory of structural subtyping of non-recursive types. Our decision procedure is based on quantifier elimination and makes use of quantifier elimination for term algebras and Feferman-Vaught construction for products of decidable structures. We also explore connections between the theory of structural subtyping of recursive types and monadic second-order theory of tree-like structures. In particular, we give an embedding of the monadic second-order theory of infinite binary tree into the first-order theory of structural subtyping of recursive types.

Boosting Fault-Tolerance in Asynchronous Message Passing Systems is Impossible

2023-03-30T03:48:41Z

Boosting Fault-Tolerance in Asynchronous Message Passing Systems is Impossible Attie, Paul C.; Lynch, Nancy A.; Rajsbaum, Sergio

Economic Mechanisms for Efficient Wireless Coexistence

2023-03-30T03:03:17Z

Economic Mechanisms for Efficient Wireless Coexistence Aftab, Omar

Automatic Detection and Repair of Errors in Data Structures

2023-03-30T03:38:08Z

Automatic Detection and Repair of Errors in Data Structures Demsky, Brian; Rinard, Martin We present a system that accepts a specification of key data structure constraints, then dynamically detects and repairs violations of these constraints. Our experience using our system indicates that the specifications are relatively easy to develop once one understands the data structures. Furthermore, for our set of benchmark applications, our system can effectively repair errors to deliver consistent data structures that allow the program to continue to operate successfully within its designed operating envelope.

A Type System and Analysis for the Automatic Extraction and Enforcement of Design Information

2023-03-30T04:08:16Z

A Type System and Analysis for the Automatic Extraction and Enforcement of Design Information Lam, Patrick; Rinard, Martin We present a new type system and associated type checker, analysis, and model extraction algorithms for automatically extracting models that capture aspects of the design of the program. Our type system enables the developer to place a _token_ on each object; this token serves as the object's representative during the analysis and model extraction. The polymorphism in our type system enables the use of general-purpose classes whose instances may serve different purposes in the computation; programmers may also hide the details of internal data structures by placing the same token on all of the objects in these data structures. Our combined type system and analysis provide the model extraction algorithms with sound heap aliasing information. Our algorithms can therefore extract both structural models that characterize object referencing relationships and behavioral models that capture indirect interactions mediated by objects in the heap. Previous approaches, in contrast, in the absence of aliasing information, have focused on control-flow interactions that take place at procedure call boundaries. We have implemented our type checker, analysis, and model extraction algorithms and used them to produce design models. Our experience indicates that it is straightforward to produce the token annotations and that the extracted models provide useful insight into the structure and behavior of the program.

A Dynamic Primary View Group Communication Service

2023-03-30T04:02:17Z

A Dynamic Primary View Group Communication Service De Prisco, Roberto; Fekete, Alan; Lynch, Nancy A.; Shvartsman, Alexander A.

Hardware Mechanisms for Memory Integrity Checking

2023-03-30T03:45:55Z

Hardware Mechanisms for Memory Integrity Checking Suh, G. Edward; Clarke, Dwaine; Gassend, Blaise; van Dijk, Marten; Devadas, Srinivas Memory integrity verification is a useful primitive when implementing secure processors that are resistant to attacks on hardware components. This paper proposes new hardware schemes to verify the integrity of untrusted external memory using a very small amount of trusted on-chip storage. Our schemes maintain incremental multiset hashes of all memory reads and writes at run-time, and can verify a {\\em sequence} of memory operations at a later time. We study the advantages and disadvantages of the two new schemes and two existing integrity checking schemes, MACs and hash trees, when implemented in hardware in a microprocessor. Simulations show that the new schemes outperform existing schemes of equivalent functionality when integrity verification is infrequent.

Offline Integrity Checking of Untrusted Storage

2023-03-30T03:57:05Z

Offline Integrity Checking of Untrusted Storage Clarke, Dwaine; Gassend, Blaise; Suh, G. Edward; van Dijk, Marten; Devadas, Srinivas

Access-Controlled Resource Discovery for Pervasive Networks

2023-03-30T03:03:29Z

Access-Controlled Resource Discovery for Pervasive Networks Raman, Sanjay; Clarke, Dwaine; Burnside, Matt; Devadas, Srinivas; Rivest, Ronald L. Networks of the future will be characterized by a variety of computational devices that display a level of dynamism not seen in traditional wired networks. Because of the dynamic nature of these networks, resource discovery is one of the fundamental problems that must be faced. While resource discovery systems are not a novel concept, securing these systems in an efficient and scalable way is challenging. This paper describes the design and implementation of an architecture for access-controlled resource discovery. This system achieves this goal by integrating access control with the Intentional Naming System (INS), a resource discovery and service location system. The integration is scalable, efficient, and fits well within a proxy-based security framework designed for dynamic networks. We provide performance experiments that show how our solution outperforms existing schemes. The result is a system that provides secure, access-controlled resource discovery that can scale to large numbers of resources and users

A Type System for Safe Region-Based Memory Management in Real-Time Java

2023-03-30T03:38:15Z

A Type System for Safe Region-Based Memory Management in Real-Time Java Salcianu, Alexandru; Boyapati, Chandrasekhar; Beebee, William S., Jr.; Rinard, Martin The Real-Time Specification for Java (RTSJ) allows a program to create real-time threads with hard real time constraints. Real-time threads use immortal memory and region-based memory management to avoid unbounded pauses caused by interference from the garbage collector. The RTSJ uses runtime checks to ensure that deleting a region does not create dangling references and that real-time threads do not access references to objects allocated in the garbage-collected heap. This paper presents a static type system that guarantees that these runtime checks will never fail for well-typed programs. Our type system therefore 1) provides an important safety guarantee for real-time programs and 2) makes it possible to eliminate the runtime checks and their associated overhead. Our system also makes several contributions over previous work on region types. For object-oriented programs, it combines region types and ownership types in a unified type system framework. For multithreaded programs, it allows long-lived threads to share objects without using the heap and without having memory leaks. For real-time programs, it ensures that real-time threads do not interfere with the garbage collector. We have implemented several programs in our system. Our experience indicates that our type system is sufficiently expressive and requires little programming overhead. We also ran these programs on our RTSJ platform. Our experiments show that eliminating the RTSJ runtime checks using a static type system can significantly decrease the execution time of a real-time program.

A Formal Venture into Reliable Multicast Territory

2023-03-30T03:44:10Z

A Formal Venture into Reliable Multicast Territory Livadas, Carolos; Lynch, Nancy A.

The Case for Exploiting Packet Loss Locality in Multicast Loss Recovery

2023-03-30T03:03:32Z

The Case for Exploiting Packet Loss Locality in Multicast Loss Recovery Livadas, Carolos; Keidar, Idit

Blueware: Bluetooth Simulator for ns

2023-03-30T03:51:15Z

Blueware: Bluetooth Simulator for ns Tan, Godfrey

Tetris is Hard, Even to Approximate

2023-03-30T03:04:59Z

Tetris is Hard, Even to Approximate Demaine, Erik D.; Hohenberger, Susan; Liben-Nowell, David

The Facility Location Problem with Concave Cost Functions

2023-03-30T03:51:14Z

The Facility Location Problem with Concave Cost Functions Hajiaghayi, Mohammad Taghi; Mahdian, Mohammad; Mirrokni, Vahab S.

Scalar Operand Networks: On-chip interconnect for ILP in Partitioned Architechures

2023-03-30T03:54:30Z

Scalar Operand Networks: On-chip interconnect for ILP in Partitioned Architechures Taylor, Michael Bedford; Lee, Walter; Amarasinghe, Saman; Agarwal, Anant

Ownership Types and Safe Lazy Upgrades in Object-Oriented Databases

2023-03-30T03:40:56Z

Ownership Types and Safe Lazy Upgrades in Object-Oriented Databases Boyapati, Chandrasekhar; Liskov, Barbara H.; Shrira, Liuba

Caches and Merkle Trees for Efficient Memory Authentication

2023-03-30T03:38:39Z

Caches and Merkle Trees for Efficient Memory Authentication Gassend, Blaise; Suh, G. Edward; Clarke, Dwaine; van Dijk, Marten; Devadas, Srinivas

Delay-Based Circuit Authentication With Application to Key Cards

2023-03-30T03:37:02Z

Delay-Based Circuit Authentication With Application to Key Cards Gassend, Blaise; Clarke, Dwaine; van Dijk, Marten; Devadas, Srinivas

Safe Runtime Downcasts With Ownership Types

2023-03-30T03:45:46Z

Safe Runtime Downcasts With Ownership Types Boyapati, Chandrasekhar; Lee, Robert; Rinard, Martin

Automatic Generation and Checking of Program Specifications

2023-03-30T04:19:50Z

Automatic Generation and Checking of Program Specifications Nimmer, Jeremy

Safe Lazy Software Upgrades in Object-Oriented Databases

2023-03-30T03:25:42Z

Safe Lazy Software Upgrades in Object-Oriented Databases Liskov, Barbara H.; Moh, Chuang-Hue; Richman, Steven; Shrira, Liuba; Chueng, Yin; Boyapati, Chandrasekhar

Combining Abstraction with Byzantine Fault-Tolerance

2023-03-30T03:08:21Z

Combining Abstraction with Byzantine Fault-Tolerance Rodrigues, Rodrigo

A Scalable Byzantine Fault Tolerant Secure Domain Name Service

2023-03-30T03:42:11Z

A Scalable Byzantine Fault Tolerant Secure Domain Name Service Ahmed, Sarah

Improving Test Suites via Generated Specifications

2023-03-30T03:17:53Z

Improving Test Suites via Generated Specifications Harder, Michael

A Trusted Third-Party Computation Service

2023-03-30T04:13:15Z

A Trusted Third-Party Computation Service Ajmani, Sameer; Morris, Robert T.; Liskov, Barbara H.

A Trusted Execution Platform for Multiparty Computation

2023-03-30T03:52:12Z

A Trusted Execution Platform for Multiparty Computation Ajmani, Sameer

Controlled Physical Unknown Functions: Applications to Secure Smartcards and Certified Execution

2023-03-30T03:26:36Z

Controlled Physical Unknown Functions: Applications to Secure Smartcards and Certified Execution Gassend, Blaise; Clarke, Dwaine; van Dijk, Marten; Devadas, Srinivas

A Double-Pulsed Set-Conditional-Reset Flip-Flop

2023-03-30T03:47:22Z

A Double-Pulsed Set-Conditional-Reset Flip-Flop Ma, Albert; Asanovi_, Krste

The IOA Simulator

2023-03-30T03:39:51Z

The IOA Simulator Kaynar, Dilsun Kirh; Chefter, Anna; Dean, Laura; Garland, Stephen J.; Lynch, Nancy A.; Ne Win, Toh; Ramírez-Robredo, Antonio

Towards An Extensible Virtual Machine

2023-03-30T03:31:52Z

Towards An Extensible Virtual Machine Boyapati, Chandrasekhar

Verifying Distributed Algorithms via Dynamic Analysis and Theorem Proving

2023-03-30T03:35:15Z

Verifying Distributed Algorithms via Dynamic Analysis and Theorem Proving Ne Win, Toh; Ernst, Michael D.

Early-Delivery Dynamic Atomic Broadcast

2023-03-30T04:27:09Z

Early-Delivery Dynamic Atomic Broadcast Bar-Joseph, Ziv; Keidar, Idit; Lynch, Nancy A.

A Type System for Preventing Data Races and Deadlocks in Java Programs

2023-03-30T03:51:21Z

A Type System for Preventing Data Races and Deadlocks in Java Programs Boyapati, Chandrasekhar; Lee, Robert; Rinard, Martin

Exponential Speedup of Fixed Parameter Algorithms K_{3,3}-minor-free or K_5-minor-free Graphs

2023-03-30T03:23:34Z

Exponential Speedup of Fixed Parameter Algorithms K_{3,3}-minor-free or K_5-minor-free Graphs Demaine, Erik D.; Hajiaghayi, Mohammad Taghi; Thilikos, Dimitrios M.

L+: Scalable Landmark Routing and Address Lookup for Multi-hop Wireless Networks

2023-03-30T04:08:33Z

L+: Scalable Landmark Routing and Address Lookup for Multi-hop Wireless Networks Chen, Benjie; Morris, Robert T.

Effects of Loss Rate on Ad Hoc Wireless Routing

2023-03-30T15:48:57Z

Effects of Loss Rate on Ad Hoc Wireless Routing DeCouto, Douglas S.J.; Aguayo, Daniel; Chambers, Benjamin A.; Morris, Robert This paper uses measurements from two deployed wireless ad hoc networks to illustrate the effects of link loss rates on routing protocol performance. Measurements of these networks show that the radio links between the majority of nodes have substantial loss rates. These loss rates are high enough to prevent existing ad hoc routing protocols from using the links. Link-level retransmission can mask high loss rates, at the cost of substantial decreases in throughput. Simulations, driven by the observed loss rates, show that the shortest paths chosen by existing routing protocols tend to find routes with much less capacity than is available along the best route. Based on these observations, we present a routing metric intended to allow routing protocols to find good routes in wireless ad hoc networks. The metric is the expected total number of transmissions required to deliver a packet along a route. This metric favors routes with high throughput and low total impact on spectrum. It is expected to perform better than existing techniques that eliminate links based on loss rate thresholds.

Write Barrier Removal by Static Analysis

2023-03-30T03:18:05Z

Write Barrier Removal by Static Analysis Zee, Karen; Rinard, Martin

Silicon Physical Unknown Functions and Secure Smartcards

2023-03-30T03:12:25Z

Silicon Physical Unknown Functions and Secure Smartcards Gassend, Blaise; Clarke, Dwaine; van Dijk, Marten; Devadas, Srinivas

Fine-Grain Dynamic Leakage Reduction

2023-03-30T04:14:54Z

Fine-Grain Dynamic Leakage Reduction Heo, Seongmoo; Barr, Kenneth; Hampton, Mark; Asanovi_, Krste

Leakage-Biased Domino Circuits for Dynamic Fine-Grain Leakage Reduction

2023-03-30T03:23:29Z

Leakage-Biased Domino Circuits for Dynamic Fine-Grain Leakage Reduction Heo, Seongmoo; Asanovi_, Krste

An Information-Theoretic Approach to Interest Making

2023-03-30T03:04:19Z

An Information-Theoretic Approach to Interest Making Koh, Waikit The Internet has brought a new meaning to the term communities. Geography is no longer a barrier to international communications. However, the paradigm of meeting new interesting people remains entrenched in traditional means; meeting new interesting people on the Internet still relies on chance and contacts. This thesis explores a new approach towards matching users in online communities in an effective fashion. Instead of using the conventional feature vector scheme to profile users, each user is represented by a personalized concept hierarchy (or an ontology) that is learnt from the user's behavior in the system. Each concept hierarchy is then interpreted within the Information Theory framework as a probabilistic decision tree. The matching algorithm uses the Kullback-Leiber distance as a measure of deviation between two probabilistic decision trees. Thus, in an online community, where a personalized concept hierarchy represents each user, the Kullback-Leiber distance imposes a full- order rank on the level of similarity of all the users with respect to a particular user in question. The validity and utility of the proposed scheme of matching users is then applied in a set of simulations, using the feature-vector-overlap measure as a baseline. The results of the simulations show that the Kullback Leiber distance, when used in conjunction with the concept hierarchy, is more robust to noise and is able to make a stronger and more distinctive classification of users into similar groups in comparison to the conventional keyword-overlap scheme. A graphical agent system that relies upon the ontology-based interest matching algorithm, called the Collaborative Sanctioning Network, is also described in this thesis.

2RegionRED: a Congestion Control Mechanism for the High Speed Internet

2023-03-30T03:40:53Z

2RegionRED: a Congestion Control Mechanism for the High Speed Internet Wang, Karen This thesis proposes a new Active Queue Management (AQM) scheme called 2RegionRED. It is superior to the classic Random Early Detection (RED) algorithm in that there is an intuitive way to set its parameters and it is self-tuning. Its design is motivated by an original principle to sustain the smallest queue possible while still allowing for maximum link utilization. 2RegionRED uses the number of competing TCPs as its measure of load. However it does not keep an explicit count. The result is a novel algorithm that adjusts the drop rate according to two regions of operation: that requiring less than and greater than one drop per round-trip time (RTT). This thesis also analyzes methods for measuring the persistent queue and proposes the ABSMIN method. Simulations of 2RegionRED using ABSMIN reveal some difficulties and insights. Basic comparisons to the Adaptive RED and Flow Proportional Queuing (FPQ) adaptive algorithms are also demonstrated through simulation

Inferring Congestion Sharing and Path Characteristics from Packet Interarrival Times

2023-03-30T03:39:47Z

Inferring Congestion Sharing and Path Characteristics from Packet Interarrival Times Katabi, Dina; Blake, Charles

Hybrid I/O Automata*

2023-03-30T15:37:37Z

Forming Scatternets from Bluetooth Personal Area Networks

2023-03-30T03:42:32Z

Forming Scatternets from Bluetooth Personal Area Networks Tan, Godfrey; Mui, Allen; Guttag, John V.; Balakrishnan, Hari There is increasing interest in wireless ad hoc networks built from portable devices equipped with short-range wireless network interfaces. This paper addresses issues related to internetworking such networks to form larger ÔøΩscatternets.ÔøΩ Within the constraints imposed by the emerging standard Bluetooth link layer and MAC protocol, we describe an efficient online topology formation algorithm, called TSF (Tree Scatternet Formation) to build scatternets. TSF connects nodes in a tree structure that simplifies packet routing and scheduling. The design allows nodes to arrive and leave arbitrarily, incrementally building the topology and healing partitions when they occur. We present simulation results that show that TSF has low tree formation latency and also generates an efficient topology for forwarding packets.

Scalable, Controlled Imagery Capture in Urban Environments

2023-03-30T04:22:15Z

Scalable, Controlled Imagery Capture in Urban Environments Teller, Seth We describe the design considerations underlying a system for scalable, automated capture of precisely controlled imagery in urban scenes. The system operates for architectural scenes in which, from every camera position, some two vanishing points are visible. It has been used to capture thousands of controlled images in outdoor environments spanning hundreds of meters. The proposed system architecture forms the foundation for a future, fully robotic outdoor mapping capability for urban areas, analogous to existing, satellite-based robotic mapping systems which acquire images and models of natural terrain. Four key ideas distinguish our approach from other methods. First, our sensor acquires georeferencing metadata with every image, enabling related images to be efficiently identified and registered. Second, the sensor acquires omni-directional images; we show strong experimental evidence that such images are fundamentally more powerful observations than conventional (narrow-FOV) images. Third, the system uses a probabilistic, projective error formulation to account for uncertainty. By treating measurement error in an appropriate depth-free framework, and by deferring decisions about camera calibration and scene structure until many noisy observations can be fused, the system achieves superior robustness and accuracy. Fourth, the system's computational requirements scale linearly in the input size, the area of the acquisition region, and the size of the output model. This is in contrast to most previous methods, which either assume constant-size inputs or exhibit quadratic running time (or worse) asymptotically. These attributes enable the system to operate in a regime of scale and physical extent which is unachievable by any other method, whether manual or automated. Consequently, it can acquire the most complex calibrated terrestrial image sets in existence, while operating faster thanany existing manual or algorithmic method.

Location Proxies and Intermediate Node Forwarding for Practical Geographic Forwarding

2023-03-30T03:42:26Z

Location Proxies and Intermediate Node Forwarding for Practical Geographic Forwarding De Couto, Douglas S.J.; Morris, Robert T.

Automatic Generation and Checking of Program Specifications

2023-03-30T04:09:32Z

Automatic Generation and Checking of Program Specifications Nimmer, Jeremy W.; Ernst, Michael D.

Roles Are Really Great!

2023-03-30T04:20:00Z

Roles Are Really Great! Kuncak, Viktor; Lam, Patrick; Rinard, Martin

On the Cost of Fault-Tolerant Consensus When There Are No Faults - A Tutorial

2023-03-30T03:23:16Z

On the Cost of Fault-Tolerant Consensus When There Are No Faults - A Tutorial Keidar, Idit; Rajsbaum, Sergio

Using precise feedback for controlling congestion in the Internet

2023-03-30T03:41:11Z

Using precise feedback for controlling congestion in the Internet Katabi, Dina; Handley, Mark

Chord: A scalable peer-to-peer lookup service for Internet applications

2023-03-30T03:55:11Z

Chord: A scalable peer-to-peer lookup service for Internet applications Stoica, Ion; Morris, Robert T.; Karger, David R.; Kaashoek, M. Frans; Balakrishnan, Hari

Client Authentication on the Web

2023-03-30T03:35:58Z

Client Authentication on the Web Fu, Kevin; Sit, Emil; Smith, Kendra; Feamster, Nick

Practical Byzantine Fault Tolerance

2023-03-30T04:23:09Z

Practical Byzantine Fault Tolerance Castro, Miguel Our growing reliance on online services accessible on the Internet demands highly-available systemsthat provide correct service without interruptions. Byzantine faults such as software bugs, operatormistakes, and malicious attacks are the major cause of service interruptions. This thesis describesa new replication algorithm, BFT, that can be used to build highly-available systems that tolerateByzantine faults. It shows, for the first time, how to build Byzantine-fault-tolerant systems that canbe used in practice to implement real services because they do not rely on unrealistic assumptionsand they perform well. BFT works in asynchronous environments like the Internet, it incorporatesmechanisms to defend against Byzantine-faulty clients, and it recovers replicas proactively. Therecovery mechanism allows the algorithm to tolerate any number of faults over the lifetime of thesystem provided fewer than 1=3 of the replicas become faulty within a small windowof vulnerability.The window may increase under a denial-of-service attack but the algorithm can detect and respondto such attacks and it can also detect when the state of a replica is corrupted by an attacker.BFT has been implemented as a generic program library with a simple interface. The BFTlibrary provides a complete solution to the problem of building real services that tolerate Byzantinefaults. We used the library to implement the first Byzantine-fault-tolerant NFS file system, BFS. TheBFT library and BFS perform well because the library incorporates several important optimizations.The most important optimization is the use of symmetric cryptography to authenticate messages.Public-key cryptography, which was the major bottleneck in previous systems, is used only toexchange the symmetric keys. The performance results show that BFS performs 2% faster to 24%slower than production implementations of the NFS protocol that are not replicated. Therefore, webelieve that the BFT library can be used to build practical systems that tolerate Byzantine faults.

Object Models, Heaps and Interpretations

2023-03-30T04:01:30Z

Object Models, Heaps and Interpretations Rinard, Martin; Kuncak, Viktor This paper explores the use of object models for specifying verifiable heap invariants. We define a simple language based on sets and relations and illustrate its use through examples. We give formal semantics of the laguage by translation into predicate calculus and interpretation of predicates in terms of objects and references in the program heap.

Perspectives on the Use of the Internet in Sri Lanka

2023-03-30T04:05:40Z

Perspectives on the Use of the Internet in Sri Lanka Shrestha, Govinda; Amarasinghe, Saman The survey examines the use of computers and the Internet in Sri Lanka from the perspective of the Internet Service Provider (ISP) members. It attempts to describe the general nature of IT use in terms of the availability, access, familiarity and general conditions associated with using computers and the Internet in the country. The survey was conducted in July 1999. Questionnaires were e-mailed to 9448 ISP members in Sri Lanka, using e-mail addresses available to us at that time. Altogether, 560 members completed and returned questionnaires via e-mail to MIT's Laboratory for Computer Science. Descriptive analysis of both quantitative and qualitative data was then conducted. Major quantitative findings include: *Over 60% of the respondents were members of their respective ISPs for two or less years, and over half had first used a computer sometime during the 1990-99 period. *Sixty-two percent of the respondents had sent 10 or more e-mails per week over the past six (or less) months, and 52% had received 15 or more e-mails per week during the same period. *Nearly half of the respondents used a computer at home, and 48% indicated 33.6K as the baud rate to connect their ISPs. *Seventy-eight percent of the respondents spent 1-9 hours per week sending and receiving e-mails, and a large majority (68%) spent 1-9 hours surfing the Web. *A majority of the respondents were positive about conditions in the workplace, such as the number and quality of opportunities for training and skill development, the quality of telecommunications facilities, and the quality and reliability of Internet connections. *An overwhelming majority of the respondents indicated that ISP subscriber fees, computer hardware and software costs, and telecommunications charges were generally high. *Most respondents were generally positive about 1) the quality of access to the Internet, 2) the quality of access to e-mails, Web pages and other Internet-based features, and 3) various benefits of Internet access. *Seventy-one percent of the respondents were male; nearly half were younger than 35, and a large majority were educated (with at least a high school diploma.) Private company employees and people in business comprised over half of the respondents. Major qualitative findings include: * It is crucially important to have faster access to information, increased communication at low costs, online-education and training, and increased efficiency in business, professional and organizational activities. * Matters of considerable concern include the low bandwidth, the high telecommunications charges, the low quality of Internet services, and the lack of organized information and databases. * Greatly needed is a raising of awareness, a change in the current regulatory environment, an open government, and a set of local information resources to support commerce.

Automatic Recovery of Camera Positions in Urban Scenes

2023-03-30T03:50:12Z

Automatic Recovery of Camera Positions in Urban Scenes Antone, Matthew E.; Teller, Seth Accurate camera calibration is crucial to the reconstruction of three-dimensional geometry and the recovery of photometric scene properties. Calibration involves the determination of intrinsic parameters (e.g. focal length, principal point, and radial lens distortion) and extrinsic parameters (orientation and position). In urban scenes and other environments containing sufficient geometric structure, it is possible to decouple extrinsic calibration into rotational and translational components that can be treated separately, simplifying the registration problem. Here we present such a decoupled formulation and describe methods for automatically recovering the positions of a large set of cameras given intrinsic calibration, relative rotations, and approximate positions. Our algorithm first estimates the directions of translation (up to an unknown scale factor) between adjacent camera pairs using point features but without requiring explicit correspondence between them. This technique combines the robustness and simplicity of a Hough transform with the accuracy of Monte Carlo expectation maximization. We then find a set of distances between the pairs that produces globally-consistent camera positions. Novel uncertainty formulations and match plausibility criteria improve reliability and accuracy. We assess our system's performance using both synthetic data and a large set of real panoramic imagery. The system produces camera positions accurate to within 5 centimeters in image networks extending over hundreds of meters.

Fine-Grained Failover Using Connection Migration

2023-03-30T03:13:54Z

Fine-Grained Failover Using Connection Migration Snoeren, Alex C.; Andersen, David G.; Balakrishnan, Hari This paper presents a set of techniques for providing fine-grained failover of long-running connections across a distributed collection of replica servers, and is especially useful for fault-tolerant and load-balanced delivery of streaming media and telephony sessions. Our system achieves connection-level failover across both local- and wide-area server replication, without requiring a front-end transport- or application-layer switch. Our approach is enabled by the recently-developed end-to-end ``connection migration'' mechanism for transport protocols such as TCP, combined with a soft-state session synchronization protocol between replica servers. The end result is a robust, fast, and fine-grained server failover mechanism that is transparent to both the client and server applications. We describe the details of our design and Linux implementation, as well as experiments with our implementation that show that this approach to failover is an attractive way to engineer robust systems for distributing long-running streams; connections suffer relatively low performance degradation even when server redirection occurs every few seconds, and overhead is negligible when compared to standard techniques. In particular, we observe the performance impact of migrating TCP connections depends on the length of time between migration and the most recent loss-recovery event.

Programming Language Techniques for Modular Router Configurations

2023-03-30T04:20:16Z

Programming Language Techniques for Modular Router Configurations Kohler, Eddie; Chen, Benjie; Kaashoek, M. Frans; Morris, Robert T.; Poletto, Massimiliano This paper applies programming language techniques to a high-level system description, both to optimize the system and to prove useful properties about it. The system in question is Click, a modular software router framework. Click routers are built from components called elements. Elements are written in C++, but the user creates a configuration using a simple, declarative data flow language. This language is amenable to data flow analysis and other conventional programming language techniques. Applied to a router configuration, these techniques have high-level results---for example, optimizing the router or verifying its high-level properties. This paper describes several programming language techniques that have been useful in practice, including optimization tools that remove virtual function calls from router definitions and remove redundant parts of adjacent routers. We also present performance results for an extensively optimized standards-compliant IP router. On conventional PC hardware, this router can forward up to 456,000 64-byte packets per second.

An Efficient Boosting Algorithm for Combining Preferences

2023-03-30T03:03:35Z

An Efficient Boosting Algorithm for Combining Preferences Iyer, Raj Dharmarajan, Jr. The problem of combining preferences arises in several applications, such as combining the results of di_x000B_erent search engines. This work describes an effcient algorithm for combining multiple preferences. We _x000C_rst give a formal framework for the problem. We then describe and analyze a new boosting algorithm for combining preferences called RankBoost. We also describe an effcient implementation of the algorithm for certain natural cases. We discuss two experiments we carried out to assess the performance of RankBoost. In the _x000C_rst experiment, we used the algorithm to combine di_x000B_erent WWW search strategies, each of which is a queryexpansion for a given domain. For this task, we compare the performance of RankBoost to the individual search strategies. The second experiment is a collaborative-filtering task for making movie recommendations. Here, we present results comparing RankBoost to nearest-neighbor and regression algorithms.

TrendFinder: Automated Detection of Alarmable Trends

2023-03-30T04:04:13Z

TrendFinder: Automated Detection of Alarmable Trends Tsien, Christine L.

System Support for Bandwidth Management and Content Adaptation in Internet Applications

2023-03-30T03:53:17Z

System Support for Bandwidth Management and Content Adaptation in Internet Applications Andersen, David; Bansal, Deccuk; Curtis, Dorothy; Seshan, Srinivasan; Balakrishnan, Hari

An Analysis of Short-Term Fairness in Wireless Media Access Protocols

2023-03-30T04:03:35Z

An Analysis of Short-Term Fairness in Wireless Media Access Protocols Koksal, Can Emre; Kassab, Hisham; Balakrishnan, Hari We investigate the problem of unfairness over short time scales in decentralized wireless media access (MAC) protocols. Motivated by experimental results over a CSMA/CA-based WaveLAN wireless LAN that shows starvation and degraded TCP performance, we see

TCP-friendly Congestion Control for Real-time Streaming Applications

2023-03-30T03:00:59Z

TCP-friendly Congestion Control for Real-time Streaming Applications Bansal, Deepak; Balakrishnan, Hari This paper introduces and analyzes a class of nonlinear congestion control algorithms called binomial algorithms, motivated in part by the needs of streaming audio and video applications for which a drastic reduction in transmission rate upon congestion i

On Building Blocks for Distributed Systems

2023-03-30T03:04:27Z

On Building Blocks for Distributed Systems De Prisco, Robert

The Static Single Information Form

2023-03-30T03:40:45Z

The Static Single Information Form Ananian, C. Scott The Static Single Information (SSI) form is a compiler intermediate representation that allows efficient sparse implementations of predicated analysis and backward dataflow algorithms. It possesses several attractive graph-theoretic properties which aid

Maps: A Compiler-Managed Memory System for Software-Exposed Architectures

2023-03-30T03:03:04Z

Maps: A Compiler-Managed Memory System for Software-Exposed Architectures Barua, Rajeev Microprocessors must exploit both instruction-level parallelism (ILP) and memory parallelism for high performance. Sophisticated techniques for ILP have boosted the ability of modern-day microprocessors to exploit ILP when available. Unfortunately, impro

QoS Preserving Totally Ordered Multicast

2023-03-30T03:38:03Z

QoS Preserving Totally Ordered Multicast Bar-Joseph, Ziv; Keidar, Idit; Anker, Tal; Lynch, Nancy A. This paper studies the Quality of Service (QoS) guarantees of totally ordered multicast algorithms. The paper shows that totally ordered multicast can coexist with guaranteed predictable delays in certain network models. The paper considers two reservatio

Compositional Pointer and Escape Analysis for Multithreaded Java Programs

2023-03-30T03:36:10Z

Compositional Pointer and Escape Analysis for Multithreaded Java Programs Rinard, Martin; Whaley, John

A Client-Server Approach to Virtually Synchronous Group Multicast: Specifications, Algorithms, and Proofs

2023-03-30T04:11:06Z

A Client-Server Approach to Virtually Synchronous Group Multicast: Specifications, Algorithms, and Proofs Keidar, Idit; Khazan, Roger This paper presents a formal design for a novel group multicast service that provides virtually synchronous semantics in asynchronous fault-prone environments. The design employs a client-server architecture in which group membership is maintained not by

Information Technology Use in Developing Countries

2023-03-30T04:13:19Z

Information Technology Use in Developing Countries Shrestha, Govinda

Group Communication Specifications: A Comprehensive Study

2023-03-30T04:25:49Z

Group Communication Specifications: A Comprehensive Study Vitenberg, Roman; Keidar, Idit; Chockler, Gregory V.; Dolev, Danny View-oriented group communication is an important and widely used building block for many distributed applications. Much current research has been dedicated to specifying the semantics and services of view-oriented Group Communication Systems (GCSs). Howe

I/O Automaton Models and Proofs for Shared-Key Communication Systems

2023-03-30T04:25:16Z

I/O Automaton Models and Proofs for Shared-Key Communication Systems Lynch, Nancy A. The combination of two security protocols, a simple shared-key communication protocol and the Diffie-Hellman key distribution protocol, is modeled formally and proved correct. The modeling is based on the I/O automaton model for distributed algorithms, an

Natural Selection and Loop Analysis

2023-03-30T03:26:25Z

Natural Selection and Loop Analysis Mohtashemi, Mojdeh

Weak Consistency: A Generalized Theory and Optimistic Implementations for Distributed Transactions

2023-03-30T03:29:10Z

Weak Consistency: A Generalized Theory and Optimistic Implementations for Distributed Transactions Adya, Atul Current commercial databases allow application programmers to trade off consistency for performance. However, existing definitions of weak consistency levels are either imprecise or they disallow efficient implementation techniques such as optimism. Rul

Portable High-Performance Programs

2023-03-30T03:03:11Z

Portable High-Performance Programs Frigo, Matteo This dissertation discusses how to write computer programs that attain both high performance and portability, despite the fact that current computer systems have different degrees of parallelism, deep memory hierarchies, and diverse processor architecture

Immediate-Mode Ray-Casting

2023-03-30T03:03:01Z

Immediate-Mode Ray-Casting Alex, John; Teller, Seth We propose a simple modification to the classical polygon rasterization pipeline that enables exact, efficient raycasting of bounded implicit surfaces without the use of a global spatial data structure bounding hierarchy. Our algorithm requires two descr

Mostly-Static Decentralized Information Flow Control

2023-03-30T03:02:54Z

Mostly-Static Decentralized Information Flow Control Myers, Andrew C. The growing use of mobile code in downloaded programs such as applets and servlets has increased interest in robust mechanisms for ensuring privacy and secrecy. Common security mechanisms such as sandboxing and access control are either too restrictive or

Performance Nonmonotonicities: A Case Study of the UltraSPARC Processor

2023-03-30T03:18:48Z

Performance Nonmonotonicities: A Case Study of the UltraSPARC Processor Kushman, Nathaniel A. Modern microprocessor architectures are very complex designs. Consequently, they exhibit many idiosyncrasies. In fact, situations exist in which the addition or removal of a single instruction changes the performance of a program by a factor of 3 to 4. I

Regions: A Scalable Infrastructure for Scoped Service Location in Ubiquitous Computing

2023-03-30T04:00:52Z

Regions: A Scalable Infrastructure for Scoped Service Location in Ubiquitous Computing Benedicto, Kathryn Flores Until recently, most efforts in service location have focused on finding local services. However, service location is also useful in large-scale networked environments containing numerous, possibly non-local services. Regions address this need for scala

Creating and Rendering Image-Based Visual Hulls

2023-03-30T03:25:05Z

Creating and Rendering Image-Based Visual Hulls Buehler, Chris; Matusik, Wojciech; McMillan, Leonard In this paper, we present efficient algorithms for creating and rendering image-based visual hulls. These algorithms are motivated by our desire to render real-time views of dynamic, real-world scenes. We first describe the visual hull, an abstract geomet

Providing QoS Guarantees in Input Buffered Crossbar Switches with Speedup

2023-03-30T03:07:44Z

Providing QoS Guarantees in Input Buffered Crossbar Switches with Speedup Charney, Anna

Dynamically Reparameterized Light Fields

2023-03-30T03:10:56Z

Dynamically Reparameterized Light Fields Isaksen, Aaron; McMillan, Leonard; Gortler, Steven J.

Teaching Policy to Computer Science Students

2023-03-30T04:02:39Z

Teaching Policy to Computer Science Students Blumenthal, Marjory S. Computing motivates more and more attention by policy-makers at all levels of government, and policy interests of all kind can touch on computer scienceÔøΩboth inspiring new research directions or constraining technology development. Understanding public p

Credible Compilers

2023-03-30T04:20:29Z

Credible Compilers Rinard, Martin C. This paper presents a new concept in compiler correctness: instead of proving that the compiler performs all of its transformations correctly, the compiler generates a proof that the transformed program correctly implements the input program. A simple pro

An Architecture for Intentional Name Resolution and Application-level Routing

2023-03-30T03:36:03Z

An Architecture for Intentional Name Resolution and Application-level Routing Adjie-Winoto, William; Schwartz, Elliot; Balakrishnan, Hari

An Integrated Congestion Management Architecture for Internet Hosts

2023-03-30T03:14:06Z

An Integrated Congestion Management Architecture for Internet Hosts Balakrishnan, Hari; Rahul, Hariharan S.; Seshan, Srinivasan This paper presents a novel framework for managing network congestion from an end-to-end perspective. Our work is motivated by several trends in traffic patterns that threaten the long-term stability of the Internet. These trends include the use of multi

Fast Place and Route Approaches for FPGAs

2023-03-30T03:02:05Z

Fast Place and Route Approaches for FPGAs Tessier, Russell G.

The Case for SRPT Scheduling in Web Servers

2023-03-30T04:21:56Z

The Case for SRPT Scheduling in Web Servers Harchol-Balter, Mor; Crovella, Mark E.; Park, SungSim

Polygonal Approximation of Voronoi Diagrams of Set of Triangles in Three Dimensions

2023-03-30T04:08:43Z

Polygonal Approximation of Voronoi Diagrams of Set of Triangles in Three Dimensions Teichmann, Marek; Teller, Seth

A Model for Window Based Flow Control Packet-Switched Networks

2023-03-30T03:20:18Z

A Model for Window Based Flow Control Packet-Switched Networks Yang, Xiaowei Recently, networks have increased rapidly both in scale and speed. Problems related to the control and management are of increasing interest. However, there is no satisfactory tool to study the behavior of such networks. The traditional event driven simul

Providing QoS Guarantees in Input Buffered Crossbar Switches with Speedup

2023-03-30T03:51:41Z

Providing QoS Guarantees in Input Buffered Crossbar Switches with Speedup Charny, Anna

Fast Thread Communication and Synchronization Mechanisms for a Scalable Single Chip Multiprocessor

2023-03-30T03:59:06Z

Fast Thread Communication and Synchronization Mechanisms for a Scalable Single Chip Multiprocessor Keckler, Stephen William

Scalable Inter-Cluster Communications Systems for Clustered Microprocessors

2023-03-30T04:08:37Z

Scalable Inter-Cluster Communications Systems for Clustered Microprocessors Jiang, Xiaohu; Yeung, Donald As workstation clusters move away from uniprocessors in favor of multiprocessors to support the increasing computational needs of distributed applications, greater demands are placed on the communication interfaces that couple individual workstations. th

Algorithms for Data-Race Detection in Multithreaded Programs

2023-03-30T03:35:57Z

Algorithms for Data-Race Detection in Multithreaded Programs Cheng, Guang-Ien Two parallel accesses to the same location, at least one of which is a write, form a race. Debugging such races is complicated by atomic critical sections. In programs without critical sections, a race is usually a bug causing nondeterminism. In programs

On Choosing a Task Assignment Policy for a Distributed Server System

2023-03-30T04:16:59Z

On Choosing a Task Assignment Policy for a Distributed Server System Harchol-Balter, Mor; Crovella, Mark E.; Murta, Cristina D. We consider a distributed server system model and ask which policy should be used for assigning tasks to hosts. In our model each host processes tasks in First-Come-First-Serve order and the task's service demand is known in advance. We consider four ta

Exploring Optimal Cost-Performance Designs for RAW processors

2023-03-30T03:24:22Z

Exploring Optimal Cost-Performance Designs for RAW processors Moritz, Csaba Andras; Yeung, Donald; Agarwal, Anant The semiconductor industry roadmap projects that advances in VLSI technology will permit more than one billion transistors on a chip by the year 2010. The MIT Raw microprocessor is a proposed architecture that strives to exploit these chip-level resource

A Model for Interactive Computation: Applications to Speech Research

2023-03-30T03:45:05Z

A Model for Interactive Computation: Applications to Speech Research McCandless, Michael Kyle The speech research community has developed numerous toolkits to support ongoing research, e.g. Sapphire, Spire, ISP, ESPS/Waves+, HTK, CSLU Toolkit, LNKNet. While these toolkits contain extensive and useful functionality, they typically offer limited en

Debugging Multithreaded Programs that Incorporate User-Level Locking

2023-03-30T03:47:15Z

Debugging Multithreaded Programs that Incorporate User-Level Locking Stark, Andrew F. A multithreaded program with a bug may behave nondeterministically, and this nondeterminism typically makes the bug hard to localize. This thesis presents a debugging tool, the Nondeterminator-2, which automatically finds certain nondeterminacy bugs in pr

Cilk: Efficient Multithreaded Computing

2023-03-30T03:09:38Z

Cilk: Efficient Multithreaded Computing Randall, Keith H.

Bounded-Error Interactive Ray Tracing

2023-03-30T03:24:40Z

Bounded-Error Interactive Ray Tracing Bala, Kavita; Dorsey, Julie; Teller, Seth

An Efficient Virtual Network Interface in the Fugu Scalable Workstation

2023-03-30T03:08:08Z

An Efficient Virtual Network Interface in the Fugu Scalable Workstation Mackenzie, Kenneth Martin A scalable workstation is one vision of a mainstream parallel computer: a machine that combines scalable, fine-grain communication facilities for parallel applications with virtual memory and pre-emptive multiprogramming to support general-purpose workloa

Integrated Shared-Memory and Message-Passing Communication in the Alewife Multiprocessor

2023-03-30T04:21:19Z

Integrated Shared-Memory and Message-Passing Communication in the Alewife Multiprocessor Kubiatowicz, John David To date, MIMD multiprocessors have been divided into two classes based on hardware communication models: those supporting shared memory and those supporting message passing. Breaking with tradition, this thesis argues that multiprocessors should integrate

Multigrain Shared Memory

2023-03-30T03:11:11Z

Multigrain Shared Memory Yeung, Donald Designers of parallel computers have to decide how to apportion a machine's resources between processing, memory, and communication. How these resources are apportioned determine the grain and balance of the resulting machine. Often, these design decisio

An Interactive Approach to the Identification and Extraction of Visual Events

2023-03-30T03:34:52Z

An Interactive Approach to the Identification and Extraction of Visual Events Stasior, William F.

An Interactive Approach to the Indentification and Extraction of Visual Events

2023-03-30T03:39:57Z

An Interactive Approach to the Indentification and Extraction of Visual Events Stasior, William F. This report describes an interactive approach to the computerized processing and interpretation of visual information. The objective is to facilitate the development of interactive applications that analyze and interpret video input. The approach is to

Frustum Casting for Progressive, Interactive Rendering

2023-03-30T03:13:26Z

Frustum Casting for Progressive, Interactive Rendering Teller, Seth; Alex, John Efficient visible surface determination algorithms have long been a fundamental goal of computer graphics. We discuss the well-known ray casting problem: given a geometric scene description, a synthetic camera, and a viewport which discretizes the camer

Planning and control in stochastic domains with imperfect information

2023-03-30T03:31:17Z

Planning and control in stochastic domains with imperfect information Hauskrechts, Milos

Speech Perception Using Real-Time Phoneme Detection: The BeBe System

2023-03-30T03:50:50Z

Speech Perception Using Real-Time Phoneme Detection: The BeBe System Sweeny, Latanya; Thompson, Patrick We define a new approach to speech recognition based on auditory perception and modeled after the human brain's tendency to automatically categorize speech sounds [House 1962; Liberman 1957]. As background, today's speech recognition systems are knowle

Boolean Compilation of Relational Specifications

2023-03-30T03:05:12Z

Boolean Compilation of Relational Specifications Jackson, Daniel A new method for analyzing relational specifications is described. A property to be checked is cast as a relational formula, which, if the property holds, has no finite models. The relational formula is translated into a boolean formula that has a model f

Decoding Reed Solomon Codes beyond the Error-Correction Diameter

2023-03-30T03:48:53Z

Decoding Reed Solomon Codes beyond the Error-Correction Diameter Sudan, Madhu

Algorithmic issues in coding theory

2023-03-30T04:26:41Z

Algorithmic issues in coding theory Sudan, Madhu

Formal Verification of Safety-Critical Hybrid Systems

2023-03-30T03:38:30Z

Formal Verification of Safety-Critical Hybrid Systems Livadas, Carolos This thesis investigates how the formal modeling and verification techniques of computer science can be used for the analysis of hybrid systems [1,2,3,4]---systems involving both discrete and continuous behavior. The motivation behind such research lies i

Automatic Extraction of Textured Vertical Facades from Pose Imagery

2023-03-30T03:07:09Z

Automatic Extraction of Textured Vertical Facades from Pose Imagery Coorg, Satvan; Teller, Seth Extracting 3-dimensional structure from real-world imagery and rendering it from unrestricted viewpoints is an important problem in computer vision, and increasingly, computer graphics. Despite many years of research, a system that automatically recovers

The Fastest Fourier Transform in the West

2023-03-30T03:56:14Z

The Fastest Fourier Transform in the West Frigo, Matteo; Johnson, Steven G.

Garbage Collection in a Large, Distributed Object Store

2023-03-30T03:29:37Z

Garbage Collection in a Large, Distributed Object Store Maheshwari, Umesh

View-based abstraction: Enhancing Maintainability and Modularity in the presence of Implementation Dependencies

2023-03-30T03:17:29Z

View-based abstraction: Enhancing Maintainability and Modularity in the presence of Implementation Dependencies Rodriguez, Luis H., Jr. This dissertation presents a new, backwards compatible, language independent, and incremental programming methodology called view-based abstraction. Unlike the well-known black-box abstraction approach, view-based abstraction enables programmers to maintain program modularity even in the presence of implementation couplings, i.e., dependencies among the code modules that rely on otherwise "hidden" implementation details not specified in the module interfaces. This dissertation also presents a transformation-based implementation of view-based abstraction, called ViewForm. ViewForm acts as a source-to-source preprocessor that automatically performs an implementation coupling expressed by the programmer. When the original code is later updated, ViewForm automatically attempts to reapply the implementation coupling to the updated code. ViewForm will modify the updated source code only if the coupling is still valid. In this way, by performing some extra work up front, the programmer performing an implementation coupling saves future programmers from having to pay for the consequences of broken modularity. To aid in writing this up-front ViewForm code, this dissertation presents a structured approach for using view-based abstraction and writing ViewForm transformations constructs. To demonstrate view-based abstraction, ViewForm is used to produce automated, performance-based implementation couplings in three example programs: an amorphous computing simulator, a conditional-probability pedigree computation, and ViewForm itself. Unlike other approaches that also use interprocedural program analyses, the results indicate that view-based abstraction is practical and scales gracefully - the extra automation increased compilation time from a typical 34%, to 40% in the worst case, despite a less than fully optimized ViewForm implementation. Each optimization required the programmer to write only 65 to 137 lines of ViewForm code for programs of size 167 lines to 7,616 lines. This work is amortized as time saved by programmers modifying the original program in the future. In all three examples, ViewForm maintained modularity by regenerating correct code when the original modules were modified - even when those modifications were to the optimization-dependent sections of the original code.

Managing Scheduled Routing with a High-level Communication Language

2023-03-30T03:46:48Z

Managing Scheduled Routing with a High-level Communication Language Metcalf, Christopher D.

An Optimized Hardware Architecture and Communication Protocol for Scheduled Communication

2023-03-30T03:52:36Z

An Optimized Hardware Architecture and Communication Protocol for Scheduled Communication Shoemaker, David

Building an Active Node on the Internet

2023-03-30T03:22:56Z

Building an Active Node on the Internet Murphy, David M.

Message-Driven Dynamics

2023-03-30T03:54:25Z

Message-Driven Dynamics Lethin, Richard Anton

HULA: An Efficient Protocol for Reliable Delivery of Messages

2023-03-30T03:15:58Z

HULA: An Efficient Protocol for Reliable Delivery of Messages Maheshwari, Umesh We present a new protocol for reliable delivery of messages over a network that might lose, duplicate, reorder, or arbitrarily delay packets. It is the first protocol that guarantees exactly-once and ordered delivery on a connection while avoidin

Experimental Study of Minimum Cut Algorithms

2023-03-30T03:42:28Z

Experimental Study of Minimum Cut Algorithms Levine, Matthew S. Recently, several new algorithms have been developed for the minimum cut problem that substantially improve worst-case time bounds for the problem. These algorithms are very different from the earlier ones and from each other. We conduct an experimental

A Model-Based Expert System for interpretation of hemodynamic data from ICU patients

2023-03-30T03:57:40Z

A Model-Based Expert System for interpretation of hemodynamic data from ICU patients Zhao, Ruilin

Revisiting the Paxos Algorithm

2023-03-30T03:27:51Z

Revisiting the Paxos Algorithm De Prisco, Roberto The Paxos algorithm is an efficient and highly fault-tolerant algorithm, devised by Lamport, for reaching consensus in a distributed system. Although it appears to be practical, it seems to be not widely known or understood. This thesis contains a new p

Relieving Hot Spots on the World Wide Web

2023-03-30T03:24:06Z

Relieving Hot Spots on the World Wide Web Panigrahy, Rina We describe a family of caching protocols for distributed networks that can be used to decrease or eliminate the occurrence of hot spots in the network. Hot spots are web sites that swamped by a large number of requests for their pages. Our protocols are

A Random Server Model for Private Information Retrieval (or Information Theoretic PIR Avoiding Database Replication

2023-03-30T03:58:05Z

A Random Server Model for Private Information Retrieval (or Information Theoretic PIR Avoiding Database Replication Gertner, Yael; Goldwasser, Shafi; Malkin, Tal Private information retrieval (PIR) schemes provide a user with information from a database while keeping his query secret from the database manager. We propose a new model for PIR, utilizing auxiliary random servers providing privacy services for databas

Efficient distributed 1 out of n oblivious transfer

2023-03-30T03:19:19Z

Efficient distributed 1 out of n oblivious transfer Gertner, Yael; Malkin, Tal

Fine-Grained Control of Java Applets Using a Simple Constraint Language

2023-03-30T04:05:32Z

Fine-Grained Control of Java Applets Using a Simple Constraint Language Mehta, Nimisha V. The use of the internet has increased extensively with a growing number of inexperienced users surfing the Web. Lurking in Web pages, Java applets are automatically executed on users' machines. As a result, popular Web browsers are understandably con

Engineering a Global Resolution Service

2023-03-30T03:27:26Z

Engineering a Global Resolution Service Slottow, Edward C. As the World Wide Web continues to balloon in size the issue of a robust information infrastructure has become increasingly important. Currently, Web links are based on fragile names that have limited life due to semantic content. Uniform Resource Na

Modularity in the Presence of Subclassing

2023-03-30T04:24:00Z

Modularity in the Presence of Subclassing Stata, Raymie Classes are harder to subclass than they need be. This report addresses this problem, showing how to design classes that are more modular and easier to subclass without sacrificing the extensibility that makes subclassing useful. In the context of singl

Demand-Based Coscheduling of Parallel Jobs on Multiprogrammed Multiprocessors

2023-03-30T03:04:21Z

Demand-Based Coscheduling of Parallel Jobs on Multiprogrammed Multiprocessors Sobalvarro, Patrick Gregory

Baring it all to Software: The Raw Machine

2023-03-30T03:43:24Z

Baring it all to Software: The Raw Machine Waingold, Elliot; Taylor, Michael; Sarkar, Vivek; Lee, Walter; Lee, Victor; Kim, Jang; Frank, Matthew; Finch, Peter; Devabhaktuni, Srikrishna; Barua, Rajeev; Babb, Jonathan; Amarasinghe, Saman; Agarwal, Anant Rapid advances in technology force a quest for computer architectures that exploit new opportunities and shed existing mechanisms that do not scale. Current architectures, such as hardware scheduled superscalars, are already hitting performance and comple

Optimism vs. Locking: A Study of Concurrency Control for Client-Server Object-Oriented Databases

2023-03-30T03:58:41Z

Optimism vs. Locking: A Study of Concurrency Control for Client-Server Object-Oriented Databases Gruber, Robert Edward Many client-server object-oriented database systems (OODBs) run applications at clients and perform all accesses on cached copies of database objects. Moving both data and computation to the clients can improve response time, throughput, and scalability.

Replication Control in Distributed B-Trees

2023-03-30T03:01:14Z

Replication Control in Distributed B-Trees Cosway, Paul R. B-trees are a commonly used data structure to associate symbols with related information, as in a symbol table or file index. The performance of B-tree algorithms is well understood for sequential processing and even concurrent processing on small-scale

Learning Algorithms with Applications to Robot Navigation and Protein Folding

2023-03-30T04:08:56Z

Learning Algorithms with Applications to Robot Navigation and Protein Folding Singh, Mona

Public-Key Cryptosystems from Lattice Reduction Problems

2023-03-30T03:23:52Z

Public-Key Cryptosystems from Lattice Reduction Problems Goldreich, Oded; Goldwasser, Shafi; Halevi, Shai We present a new proposal for a trapdoor one-way function, from which we derive public-key encryption and digital signatures. The security of the new construction is based on the conjectured computational difficulty of lattice-reduction proble

Code Importing Techniques for Fast, Safe Client/Server Access

2023-03-30T03:39:16Z

Code Importing Techniques for Fast, Safe Client/Server Access Bank, Joseph A.

The Cilk System for Parallel Multithreaded Computing

2023-03-30T03:23:37Z

The Cilk System for Parallel Multithreaded Computing Joerg, Christopher Frank

On Consulting a Set of Experts and Searching

2023-03-30T04:11:22Z

On Consulting a Set of Experts and Searching Galperin, Igal Two chapters of this thesis analyze expert consulting problemas via game theoretic models; the first points out a close connectionn between the problem of consulting a set of experts and the problem of searching. The last chapter presents a solution to th

Partitioned Garbage Collection of a Large Object Store

2023-03-30T04:21:17Z

Partitioned Garbage Collection of a Large Object Store Maheshwari, Umesh; Liskov, Barbara H. This paper describes a new garbage collection scheme for large persisten object stores that makes efficient use of the disk and main memory. The heap is divided into partitions that are collected independently using information about inter-partit

Shared Memory Versus Message Passing for Iterative Solution of Sparse, Irregular Problems

2023-03-30T04:21:58Z

Shared Memory Versus Message Passing for Iterative Solution of Sparse, Irregular Problems Chong, Frederic T.; Agarwal, Anant The benefits of hardware support for shared memory versus those formessage passing are difficult to evaluate without an in-depth study ofreal applications on a common platform. We evaluate the communicationmechanisms of the MIT Alewife machine, a multipr

The Computer Science Technical Report (CS-TR) Project: Considerations from the Library Perspective

2023-03-30T03:01:18Z

The Computer Science Technical Report (CS-TR) Project: Considerations from the Library Perspective Anderson, Greg; Lasher, Rebecca; Reich, Vicky In 1992 the Advanced Research Projects Agency (ARPA) funded a three year grant to investigate the questions related to large-scale, distributed, digital libraries. The award focused research on Computer Science Technical Reports (CS-TR) and was granted to

Efficient Garbage Collection for Large Object-Oriented Databases

2023-03-30T04:26:27Z

Efficient Garbage Collection for Large Object-Oriented Databases Ng, Tony C. This thesis presents the design of an efficient garbage collection scheme for large, persistent object-oriented databases in a client-server environment. The scheme uses a partitioned approach. A database is divided into disjoint partitions and each parti

A Security Model for the Information Mesh

2023-03-30T03:53:15Z

A Security Model for the Information Mesh Condell, Matthew N. Many distributed systems that are currently being designed are object based. These sytems require a model for authentication and access control which conforms to the object model. They need a model that allows objects to control their own security. In

Encapsulated Key Escrow

2023-03-30T04:09:22Z

Encapsulated Key Escrow Bellare, Mihir; Goldwasser, Shafi

Phonological Parsing for Bi-directional Letter-to-Sound/Sound-to-Letter Generation

2023-03-30T03:04:12Z

Phonological Parsing for Bi-directional Letter-to-Sound/Sound-to-Letter Generation Meng, Helen Mei-Ling This thesis proposes a unified framework for integrating a variety of linguistic knowledge sources for representing speech, in order to facilitiate their concurrent utilization in spoken language systems. The feasibility of the proposed methodology is de

On the Structure of the Scaffolding Core of Bacteriophage T4 and Its Role in Head Length

2023-03-30T03:53:49Z

On the Structure of the Scaffolding Core of Bacteriophage T4 and Its Role in Head Length Berger, Bonnie A.; Hoest, Gunnar W.; Paulson, James R.; Shor, Peter W.

Correctness of Vehicle Control Systems: A Case Study

2023-03-30T04:08:49Z

Correctness of Vehicle Control Systems: A Case Study Weinberg, Henri B.

Time-lock Puzzles and Timed-release Crypto

2023-03-30T03:41:17Z

Time-lock Puzzles and Timed-release Crypto Rivest, Ronald L.; Shamir, Adi; Wagner, David A. Our motivation is the notion of ``timed-release crypto,'' where the goal is to encrypt a message so that it can not be decrypted by anyone, not even the sender, until a pre-determined amount of time has passed. The goal is to ``send information into the

Translucent Cyrptography: An Alternative to Key Escrow, and its Implementation via Fractional Oblivious Transfer

2023-03-30T03:53:21Z

Translucent Cyrptography: An Alternative to Key Escrow, and its Implementation via Fractional Oblivious Transfer Bellare, Mihir; Rivest, Ronald L.

Adaptively Secure Multi-party Computation

2023-03-30T03:19:35Z

Adaptively Secure Multi-party Computation Canetti, Ran; Feige, Uri; Goldreich, Oded; Naor, Moni A fundamental problem in designing secure multi-party protocols is how to deal with adaptive adversaries (i.e., adversaries that may choose the corrupted parties during the course of the computation), in a setting where the channels are insecure and secur

A Theory of Clock Synchronization

2023-03-30T03:15:14Z

A Theory of Clock Synchronization Patt, Boaz We consider the problem of clock synchronization in a system with uncertain message delays and clocks with bounded drift. To analyze this classical problem, we introduce the concept of synchronization graphs, and show that the tightest achievable synchron

Admission Control and Routing: Theory and Practice

2023-03-30T04:15:26Z

Admission Control and Routing: Theory and Practice Gawlick, Rainer Emerging high speed Broadband Integrated Services Digital Networks (B-ISDN) will carry traffic for services such as video-on-demand and video teleconferencing, which require resource reservation along the path on which the traffic is sent. As a result, su

Identifying and Merging Related Bibliographic Records

2023-03-30T03:12:55Z

Identifying and Merging Related Bibliographic Records Hylton, Jeremy A. Bibliographic records freely available on the Internet can be used to construct a high-quality, digital finding aid that provides the ability to discover paper and electronic documents. The key challenge to providing such a service is integrating mixed-

Executing Multithreaded Programs Efficiently

2023-03-30T03:05:07Z

Executing Multithreaded Programs Efficiently Blumofe, Robert D. This thesis presents the theory, design, and implementation of Cilk (pronounced "silk") and Cilk-NOW. Cilk is a C-based language and portable runtime system for programming and executing multithreaded parallel programs. Cilk-NOW is an implementation of

Modeling and Verification of Randomized Distributed Real -Time Systems

2023-03-30T04:21:49Z

Modeling and Verification of Randomized Distributed Real -Time Systems Segala, Roberto Randomization is an excellent tool for the design of distributed algorithms, sometimes yielding efficient solutions to problems that are inherently complex, or even unsolvable, in the setting of deterministic algorithms. However, this tool has a price: e

High-Performance All-Software Distributed Shared Memory

2023-03-30T03:38:01Z

High-Performance All-Software Distributed Shared Memory Johnson, Kirk L. The C Region Library (CRL) is a new all-software distributed shared memory (DSM) system. CRL requires no special compiler, hardware, or operating system support beyond the ability to send and receive messages between processing nodes. It provides a simp

Aurora at MIT

2026-02-05T21:13:16Z

Aurora at MIT Clark, David D; Houh, Henry; Tennenhouse, David L.

Decentralized Channel Management in Scalable Multihop Spread-Spectrum Packet Radio Networks

2023-03-30T04:18:38Z

Decentralized Channel Management in Scalable Multihop Spread-Spectrum Packet Radio Networks Shepard, Timothy Jason This thesis addresses the problems of managing the transmissions of stations in a spread-spectrum packet ratio network so that the system can remain effective when scaled to millions of nodes concentrated in a metropolitan area. The principal difficulty

Theta Reference Manual

2023-03-30T04:06:37Z

Theta Reference Manual Liskov, Barbara; Curtis, Dorothy; Day, Mark; Ghemawat, Sanjay; Gruber, Robert; Johnson, Paul; Myers, Andrew C.

Lottery and Stride Scheduling: Flexible Proportional-share Resource Management

2023-03-30T03:22:02Z

Lottery and Stride Scheduling: Flexible Proportional-share Resource Management Waldspurger, Carl A. This thesis presents flexible abstractions for specifying resource management policies, together with efficient mechanisms for implementing those abstractions. Several novel scheduling techniques are introduced, including both randomized and deterministi

The Modified Object Buffer: A Storage Management Technique for Object-Oriented Databases

2023-03-30T03:56:38Z

The Modified Object Buffer: A Storage Management Technique for Object-Oriented Databases Ghemawat, Sanjay

Dynamic Computation Migration in Distributed Shared Memory Systems

2023-03-30T04:14:06Z

Dynamic Computation Migration in Distributed Shared Memory Systems Hsieh, Wilson Cheng-Yi

Reactive Synchronization Algorithms for Multiprocessors

2023-03-30T04:20:58Z

Reactive Synchronization Algorithms for Multiprocessors Lim, Beng-Hong Efficient synchronization algorithms are hard to design because their performance depends on run-time factors that are hard to predict. In particular, the designer has a choice of protocols to implement the synchronization operation, and a choice of wait

Restricted Branching Programs and Hardware Verification

2023-03-30T03:45:38Z

Restricted Branching Programs and Hardware Verification Ponzio, Stephen J. Recent developments in the field of digital design and hardware verification have found great use for restricted forms of branching programs. In particular, oblivious read-once branching programs (also called "OBDD's") are central to a very common techni

Computationally Efficient Error-Correcting Codes and Holographic Proofs

2023-03-30T04:26:01Z

Computationally Efficient Error-Correcting Codes and Holographic Proofs Spielman, Daniel Alan We present computationally efficient error-correcting codes and holographic proofs.Our error-correcting codes are asymptotically good and can be encoded and decoded in linear time.Our construction of holographic proofs provide, for every proof of any theo

Link Architecture for a Global Information Infrastructure

2023-03-30T03:36:41Z

Link Architecture for a Global Information Infrastructure Van Dyke, Jeffrey R.

Increasing Cross-Domain Call Batching Using Promises and Batched Control Structures

2023-03-30T03:37:39Z

Increasing Cross-Domain Call Batching Using Promises and Batched Control Structures Zondervan, Quinton Y. In a client-server system, it may be possible for the client to corrupt server data through unsafe access methods or programming error. A common method for protecting the server data is to separate the client and server into distinct protection domains,

Noise Tolerant Algorithms for Learning and Searching

2023-03-30T03:41:46Z

Noise Tolerant Algorithms for Learning and Searching Aslam, Javed Alexander We consider the problem of developing robust algorithms which cope with noisy data. In the Probably Approximately Correct model of machine learning, we develop a general technique which allows nearly all PAC learning algorithms to be converted into highly

Quantitative Performance Modeling of Scientific Computations

2023-03-30T04:26:06Z

Quantitative Performance Modeling of Scientific Computations Toledo, Sivan Abraham The first part of the thesis demonstrates that the performance of programs can be predicted accurately, automatically, and rapidly using a method called benchmapping. The key aspects benchmapping are: automatic creation of detailed performance models, pr

Reducing Synchronization Overhead in Parallel Simulation

2023-03-30T04:02:25Z

Reducing Synchronization Overhead in Parallel Simulation Legedza, Ulana Synchronization is often the dominant cost in conservative parallel simulation, particularly in simulations of parallel computers, in which low-latency simulated communication requires frequent synchronization. This thesis presents local barriers and pre

Connecting Homes to the Internet: An Engineering Cost Model of Cable vs. ISDN

2023-03-30T03:11:25Z

Connecting Homes to the Internet: An Engineering Cost Model of Cable vs. ISDN Gillett, Sharon Eisner Using the World Wide Web at 28.8 Kbps (or less) can be a frustrating experience: a multimedia page that takes a fraction of a second to download at Ethernet speeds takes many seconds at modem rates. Two enhancements to existing infrastructure have the pot

An Interchange Standard and System for Browsing Digital Documents

2023-03-30T03:28:07Z

An Interchange Standard and System for Browsing Digital Documents Kass, Andrew Jonathan With the advent of fast global digital communication networks, information will increasingly be delivered in electronic form. In addition, as libraries become increasingly more computerized, not just card catalogs but entire books will be stored on-line.

Client Cache management in a Distributed Object Database

2023-03-30T04:00:27Z

Client Cache management in a Distributed Object Database Day, Mark Stuart A distributed object database stores persistently at servers. Applications run on client machines, fetching objects into a client-side cache of objects. If fetching and cache management are done in terms of objects, rather than fixed-size units such as

Randomness Versus Non-Determinism in Distributed Computing

2023-03-30T03:57:33Z

Randomness Versus Non-Determinism in Distributed Computing Saias, Alain Isaac This thesis is devoted to the analysis and illustration of the effects of the interplay between randomness and non-determinism in randomized computing. Using ideas from game theory , we provide a general model for randomized computing which formalizes th

Quickstep: A System for Performance Monitoring and Debugging Parallel Applications on the Alewife Multiprocessor

2023-03-30T03:07:11Z

Quickstep: A System for Performance Monitoring and Debugging Parallel Applications on the Alewife Multiprocessor Mitra, Sramana

A Distributed Programming System for Media Applications

2023-03-30T04:16:14Z

A Distributed Programming System for Media Applications Phillips, Brent M.

Functional Encapsulation and Type Reconstruction in a Strongly-typed, Polymorphic Language

2023-03-30T04:25:40Z

Functional Encapsulation and Type Reconstruction in a Strongly-typed, Polymorphic Language Gupta, Shail Aditya

A Statistical Approach to Language Modelling for the ATIS Problem

2023-03-30T03:40:57Z

A Statistical Approach to Language Modelling for the ATIS Problem Koppelman, Joshua D.

Synchronized MIMD Computing

2023-03-30T04:23:36Z

Synchronized MIMD Computing Kuszmaul, Bradley C. Fast global synchronization provides simple, efficient solutions to many of the system problems of parallel computing. It achieves this by providing composition of both performance and correctness. If you understand the performance and meaning of parall

Mechanisms and Interfaces for Software-Extended Coherent Shared Memory

2023-03-30T04:15:43Z

Mechanisms and Interfaces for Software-Extended Coherent Shared Memory Chaiken, David L. Software-extended systems use a combination of hardware and software to implement shared memory on large-scale multiprocessors. Hardware mechanisms accelerate common-case accesses, while software handles exceptional events. This dissertation proposes, d

Small-Depth Counting Networks and Related Topics

2023-03-30T03:41:31Z

Small-Depth Counting Networks and Related Topics Klugerman, Michael Richard

Statistical Trajectory Models for Phonetic Recognition

2023-03-30T03:51:56Z

Statistical Trajectory Models for Phonetic Recognition Goldenthal, William David The main goal of this work is to develop an alternative methodology for acoustic-phonetic modelling of speech sounds. The approach utilizes a segment-based framework to capture the dynamical behavior and statistical dependencies of the acoustic attribute

On-Line Algorithms for Robot Navigation and Server Problems

2023-03-30T04:11:24Z

On-Line Algorithms for Robot Navigation and Server Problems Kleinberg, Jon M.

An Interactive Programming System for Media Computation

2023-03-30T03:03:40Z

An Interactive Programming System for Media Computation Wetherall, David J. As digital video is manipulated by increasingly powerful computers, many new applications are becoming viable. This report investigates the programming language aspects of controlling such video applications. It presents the design, implementation, and

The Structure of Near-minimum Edge Cuts

2023-03-30T04:16:47Z

The Structure of Near-minimum Edge Cuts Benczúr, András A.

Serializing Parallel Programs by Removing Redundant Computation

2023-03-30T03:01:17Z

Serializing Parallel Programs by Removing Redundant Computation Ernst, Michael D.

A Programming system for the Dynamic Manipulation of Temporally Sensitive Data

2023-03-30T03:07:42Z

A Programming system for the Dynamic Manipulation of Temporally Sensitive Data Lindblad, Christopher J. In computer-participative multimedia applications, the computer not only manipulates media, but also digests it and performs independent actions based on media content. In this report I discuss an approach to the design of environments to support the dev

Failsafe Key Escrow

2023-03-30T04:17:50Z

Failsafe Key Escrow Kilian, Joseph; Leighton Frank Thomson

A Scheme Shell

2023-03-30T03:54:43Z

A Scheme Shell Shivers, Olin

Time Optimal Self-Stabilizing Spanning Tree Algorithms

2023-03-30T03:10:20Z

Time Optimal Self-Stabilizing Spanning Tree Algorithms Aggarwal, Sudhanshu Madan

An Integrated Approach to Dynamic Decision Making under Uncertainty

2023-03-30T04:15:14Z

An Integrated Approach to Dynamic Decision Making under Uncertainty Leong, Tze-Yun

Global Partitioning of Parallel loops and Data Arrays for Caches and Distributed Memory in Multiprocessors

2023-03-30T03:46:15Z

Global Partitioning of Parallel loops and Data Arrays for Caches and Distributed Memory in Multiprocessors Barua, Rajeev K.

Using Specifications to Check Source Code

2023-03-30T03:52:07Z

Using Specifications to Check Source Code Evans, David

Automatic Acquisition of Language Models for Speech Recognition

2023-03-30T03:00:50Z

Automatic Acquisition of Language Models for Speech Recognition McCandless, Michael Kyle

Transaction Management for Mobile Objects Using Optimistic Concurrency Control

2023-03-30T03:09:04Z

Transaction Management for Mobile Objects Using Optimistic Concurrency Control Adya, Atul We present computationally efficient error-correcting codes and holographic proofs. Our error-correcting codes are asymptotically good and can be encoded and decoded in linear time. Our construction of holographic proofs provide, for every proof of any t

A Safe, Efficient Object Database Interface Using Batched Futures

2023-03-30T04:18:17Z

A Safe, Efficient Object Database Interface Using Batched Futures Bogle, Phillip Lee For many systems such as operating systems and databases it is important to run client code in a separate protection domain so that it cannot interfere with the correct operation of the system. Clients communicate with the server by making cross domain c

Time Surveying: Clock Synchronization over packet Networks

2023-03-30T04:12:19Z

Time Surveying: Clock Synchronization over packet Networks Troxel, Gregory D.

Investigation of a Preemptive Network Architecture

2023-03-30T03:42:04Z

Investigation of a Preemptive Network Architecture Lefelhocz, Christopher James Two network architectures, cell and packet, form the basis of most high bandwidth network research. If analyzed from the perspective of building a switch, both architectures have unique advantages. The preemptive architecture described herein proposes

Formal Specification Techniques for Promoting Software Modularity, Enhancing Documentation, and Testing Specifications

2023-03-30T03:11:44Z

Formal Specification Techniques for Promoting Software Modularity, Enhancing Documentation, and Testing Specifications Tan, Yang Meng This thesis presents three ideas. First, it presents a novel use of formal specification to promote a programming style based on specified interfaces and data abstraction in a programming language that lacks such supports. Second, it illustrates the uses of claims about specifications.

Observing "True" Concurrency

2023-03-30T03:29:26Z

Observing "True" Concurrency Jategaonkar, Lalita A. In concurrent process theory, processors are often modeled by state machines and Petri Nets. Algebraic process theories based on state machines, exemplified by Milner's CCS and Hoare's CSP, have been more fully developed than Net-based theories, but are inadequate for modeling "true" concurrency concepts such as non-atomic actions, action refinement, locality of actions, and multithreadedness.

Efficient Implementation of High-Level Languages on User-Level Communications Architectures

2023-03-30T03:01:10Z

Efficient Implementation of High-Level Languages on User-Level Communications Architectures Hsieh, Wilson C.; Johnson, Kirk L.; Kaashoek, M. Frans; Wallach, Deborah A.; Weihl, William E. User-level communication architectures --- parallel architectures that give user code direct but protected access to the network --- provide communication performance that is an order of magnitude higher than previous-generation message-passing architectures. Unfortunately, in order to take advantage of his level of performance, programmers must concern themselves with low-level issues that are often hardware dependent (e.g., what primitives to use for large and small data transfers, and either to use interrupts or polling).

Cellular Automata Methods in Mathematical Physics

2023-03-30T03:28:26Z

Cellular Automata Methods in Mathematical Physics Smith, Mark Andrew Cellular automata (CA) are fully discrete, spatially-distributed dynamical systems which can serve as an alternative framework for mathematical descriptions of physical systems. Furthermore, they constitute intrinsically parallel models of computation which can be efficiently realized with special-purpose cellular automata machines.

A Timing Analysis and Optimization System for Level-clocked Circuitry

2023-03-30T03:57:47Z

A Timing Analysis and Optimization System for Level-clocked Circuitry Papaefthymiou, Marios Christos This thesis investigates timing analysis and optimization issues in synchronous circuitry. The major thrust of our work is a collection of provably correct and efficient algorithms that perform a variety of architectural-level operations on level-clocked

Guardian Angel: Patient-Centered Health Information Systems

2023-03-30T03:03:24Z

Guardian Angel: Patient-Centered Health Information Systems Szolovits, Peter; Doyle, Jon; Long, William J.; Kohane, Isaac; Pauker, Stephen G.

Distributing Information for Collaborative Filtering on Usenet Net News

2023-03-30T03:48:40Z

Distributing Information for Collaborative Filtering on Usenet Net News Maltz, David A. As part of the Information Revolution," the amount of raw information available to computer users has increased as never before. Unfortunately , there has been a corresponding jump in the amount of unrelated information users must search through in order

The Vidboard:A Video Capture and Processing Peripheral for the ViewStation System

2023-03-30T03:49:43Z

The Vidboard:A Video Capture and Processing Peripheral for the ViewStation System Adam, Joel F.; Tennenhouse, David L. With the growth of multimedia applications, video is increasingly being handled within the computing environment. Since video presents serious technological challenges to the current generation of personal computers and networks, other systems based on t

An Algorithm for Rate Allocation in a Packet-Switching Network With Feedback

2023-03-30T03:07:04Z

An Algorithm for Rate Allocation in a Packet-Switching Network With Feedback Charny, Anna As the speed and complexity of computer networks evolve, sharing network resources becomes increasingly important. thus, the issue of how to allocate the available bandwidth among the multitude of users needs to be addressed. Such allocation needs to be

Function-Based Indexing for Object-Oriented Databases

2023-03-30T03:51:39Z

Function-Based Indexing for Object-Oriented Databases Hwang, Deborah Jing-Hwa Object-oriented databases should support queries over user-defined sets based on properties computed using user-defined functions. This dissertation presents a new function-based indexing scheme to make these queries run faster. These indexes are diffic

Fast Object Operations in a Persistent Programming System

2023-03-30T03:46:41Z

Fast Object Operations in a Persistent Programming System Myers, Andrew C.

Exploiting Specifications to Improve Program Performance

2023-03-30T03:15:46Z

Exploiting Specifications to Improve Program Performance Vandevoorde, Mark T. Although programmers benefit from interface specifications when reasoning about programs, existing compilers do not. In this thesis, I discuss how to incorporate specifications into a programming language to improve performance. I use specifications in

Run-time Thread Management for Large-Scale Distributed-Memory Multiprocessors

2023-03-30T04:10:31Z

Run-time Thread Management for Large-Scale Distributed-Memory Multiprocessors Nussbaum, Daniel Effective thread management is crucial to achieving good performance on large-scale distributed-memory multiprocessors that support dynamic threads. For a given parallel computation with some associated task constraints imposed by the task graph, a thread-management algorithm produces a running schedule as output, subject to the precedence constraints imposed by the task graph and the constraints imposed by the interprocessor communications network.

compiler analysis to implement point-to-point synchronization in parallel programs

2023-03-30T03:41:55Z

compiler analysis to implement point-to-point synchronization in parallel programs Nguyen, John The shared-memory data-parallel model presents an attractive interface for programming multiprocessors by allowing for easy management of parallel tasks while hiding details of the underlying machine architecture.

Closing the Window of Vulnerability in Multiphase memory transaction: The alewife transaction store

2023-03-30T04:17:53Z

Closing the Window of Vulnerability in Multiphase memory transaction: The alewife transaction store Kubiatowicz, John David Multiprocessor architects have begun to explore several mechanisms such as prefetching, context-switching and software-assisted dynamic cache-coherence, which transform single-phase memory transactions in conventional memory systems into multi-phase operations.

Automatic language Identification Using a Segment-Based Approach

2023-03-30T03:49:45Z

Automatic language Identification Using a Segment-Based Approach Hazen, Timothy J. Automatic language Identification (ALI) is the problem of automatically identifying the language of an utterance through the use of a computer. In 1977, House and Neuburg proposed an approach to ALI which focused on the phonotactic constraints of different languages.

Correctness of Communications Protocols, A case Study

2023-03-30T03:15:28Z

Correctness of Communications Protocols, A case Study Søgaard-Andersen, Jørgen; Lynch, Nancy A.; Lampson, Butler W. During the past few years, the technology for formal specification and verification of communication protocols has matured to the point where we believe that it now provides practical assistance for protocol design and validation.

Correctness Proof for a Network Synchronizer

2023-03-30T03:15:41Z

Correctness Proof for a Network Synchronizer Devarajan, Harish; Fekete, Alan; Lynch, Nancy A.; Shrira, Liuba In this paper we offer a formal, rigorous proof of the correctness of Awerbuch's algorithm for network synchronization [1]. We specify both the algorithm and the correctness condition using the I/O automaton model.

Liveness in Timed and Untimed Systems

2023-03-30T03:24:56Z

Liveness in Timed and Untimed Systems Gawlick, Rainer; Segala, Roberto; Søgaard-Andersen, Jørgen; Lynch, Nancy A. When proving the correctness of algorithms in distributed systems, one generally considers safety conditions and liveness conditions. The Input /Output (I/)0 automaton model and its timed version have used successfully, but have focused on safety conditions and on a restricted from of liveness called fairness.

Virtual Wires: Overcoming Pin Limitations in FPGA-based Logic Emulation

2023-03-30T03:44:32Z

Virtual Wires: Overcoming Pin Limitations in FPGA-based Logic Emulation Babb, Jonathan William Existing FPGA-based logic emulators are limited by inter-chip communication bandwidth, resulting in low gate utilization (10 to 20 percent of usable gates). This resource imbalance increases the number of chips needed to emulate a particular logic design and thereby decreases emulation speed, since signals must cross more chip boundaries.

Reordering with Hindsight

2023-03-30T03:03:08Z

Reordering with Hindsight Spiers, Bradford T. This report presents the reordering technique for parallel debugging. This technique is useful for debugging ordering errors, caused when actions a programmer meant to occur in a specific order occur in a different, unintended order.

Self-stabilization By Local Checking and Correction

2023-03-30T03:49:37Z

Self-stabilization By Local Checking and Correction Varghese, George A self-stabilizing protocol begins to behave correctly in bounded time, no matter what state it starts in. Self-stabilization abstracts the ability to tolerate arbitrary faults that stop. This thesis describes a simple paradigm called local checking and correction for the design of stabilizing network protocols.

Cache Performance of Garbage-collected Programming Languages

2023-03-30T03:55:54Z

Cache Performance of Garbage-collected Programming Languages Reinhold, Mark B. As processor speeds continue to improve relative to main-memory access times, cache performance is becoming an increasingly important component of program performance.

Structured Video: A Data Type with Content-based Access

2023-03-30T03:44:57Z

Structured Video: A Data Type with Content-based Access Duda, Andrzej; Weiss, Ron We describe structured video, a general video data model allowing free form annotation, composition, and content-based access to video segments. The structured video abstraction provides an efficient means of organizing and manipulating video data by assigning logical representations to the underlying video streams and their contents.

Fair Cryptosystems

2023-03-30T03:35:46Z

Fair Cryptosystems Micali, Silvio

A Content Routing System for Distributed Information Systems

2023-03-30T03:42:20Z

A Content Routing System for Distributed Information Systems Sheldon, Mark A.; Duda, Andrzej; Weiss, Ron; O'Toole, James; Gifford, David K. We describe the first system that provides query based associative access to the contents of distributed information servers. Queries describe desired object attributes, and are automatically forwarded to servers that contain relevant information.

I-95 The Information Market

2023-03-30T03:08:28Z

I-95 The Information Market

Distributed Garbage Collection in a Client-server, Transaction, Persistent Object System

2023-03-30T03:57:12Z

Distributed Garbage Collection in a Client-server, Transaction, Persistent Object System Maheshwari, Umesh We present a design for distributed garbage collection in a object-oriented database system called Thor. Garbage collection in Thor is different from that in conventional distributed systems because Thor has a client-server architecture, in which clients fetch copies of objects from multiple servers ans run transactions.

Implementing Orthogonal Persistence: A Simple Optimization Based on Replicating Collection

2023-03-30T03:46:54Z

Implementing Orthogonal Persistence: A Simple Optimization Based on Replicating Collection Nettels, Scott; O'Toole James

Concurrent Garbage Collection of Persistent Heaps

2023-03-30T03:36:24Z

Concurrent Garbage Collection of Persistent Heaps O'Toole, James; Nettles, Scott; Gifford, David K. We describe the first concurrent compacting garbage collector for a persistent heap. Client threads read and write the heap in primary memory, and can independently commit or about their write operations.

Real-time Replication GC: An Implementation Report

2023-03-30T03:57:04Z

Real-time Replication GC: An Implementation Report O'Toole, James; Nettles, Scott

Logical Disk: A Simple New Approach to Improving File System Performance

2023-03-30T03:41:15Z

Logical Disk: A Simple New Approach to Improving File System Performance de Jonge, Wiebren; Kaashoek, M. Frans; Hsieh, Wilson C. Making a file system efficient usually requires extensive modifications. For example, making a file system log-structured requires the introduction of new data structures that are tightly coupled with the general file system code.

An Evaluation of Multiprocessor Support for Fine-grain Synchronization in Preconditioned Conjugate Gradient

2023-03-30T03:37:14Z

An Evaluation of Multiprocessor Support for Fine-grain Synchronization in Preconditioned Conjugate Gradient Yeung, Donald This thesis explores the use of fine-grain synchronization in the preconditioned conjugate gradient (PCG) method using the modified incomplete Cholesky factorization of the coefficient matrix as a preconditioner.

The Category of Functors from State Shapes to Bottomless CPOs in Adequate for Block Structure

2023-03-30T03:01:05Z

The Category of Functors from State Shapes to Bottomless CPOs in Adequate for Block Structure Lent, Arthur Franklin We present a programming language EoA, which embodies what Reynolds has described as the ``essence of ALGOL.'' In particular, EoA allows higher-order procedures and the declaration of block structured local variables.

A Constructive Approach to Artificial Intelligence Reexamined

2023-03-30T04:03:27Z

A Constructive Approach to Artificial Intelligence Reexamined Ramstad, Robert Matthew Made-Up Minds: A Constructivist Approach to Artificial Intelligence, a Ph.D. thesis by Gary Drescher (MIT, Computer Science, September 1989) and a book published by MIT Press (1991) describe a learning system which controls a simulated robot and gathers information about causes and effects for various actions within the software simulated world the robot inhabits.

Family Values: A Beahvior Notion of Subtyping

2023-03-30T04:01:13Z

Family Values: A Beahvior Notion of Subtyping Liskov, Barbara; Wing, Jeannette M.

A History of CLU

2023-03-30T03:10:29Z

A History of CLU Liskov, Barbara H. The idea of a data abstraction has had a significant impact on the development of programming languages and on programming methodology. CLU was the first implemented programming language to provide direct linguistic support for data abstraction.

A Process Algebraic View of I/O Automata

2023-03-30T03:36:32Z

A Process Algebraic View of I/O Automata Segala, Roberto The Input/Output Automata formalism of Lynch and Tuttle is a widely used framework for the specification and verification of concurrent algorithms. Unfortunately, it has never been provided with an algebraic characterization, a formalization which has been fundamental for the success of theories like CSP, CCP and ACP.

Concurrent Timestamping Made Simple

2023-03-30T03:43:55Z

Concurrent Timestamping Made Simple Gawlick, Rainer Concurrent Timestamp Systems (CTSS) allow processes to temporally order concurrent events in an asynchronous shared memory system. Bounded memory constructions of a CTSS are extremely powerful tools for concurrency control, and are the basis for solutions to many coordination problems including mutual exclusion, randomized consensus, and multiwriter multireader atomic registers.

Compiler-directed Storage Reclamation Using Object Lifetime Analysis

2023-03-30T04:09:44Z

Compiler-directed Storage Reclamation Using Object Lifetime Analysis Hicks, James Edward, Jr. Many heap-oriented languages such as Lisp and Id depend on run-time garbage collection to reclaim storage. Garbage collection can be a significant run-time expense, especially for functional languages that tend to allocate structures often.

Managing Storage for Multithreaded Computations

2023-03-30T03:00:42Z

Managing Storage for Multithreaded Computations Blumofe, Robert D. Multithreading has become a dominant paradigm in general purpose MIMD parallel computation. To execute a multithread computation on a parallel computer, a scheduler must order and allocate threads to run on the individual processors.

Performance Assertion Checking

2023-03-30T03:25:53Z

Performance Assertion Checking Perl, Sharon Esther Performance assertion checking is an approach to describing and monitoring the performance of complex software systems. The idea is simple: system implementors write assertions that capture their expectations for performance, the system is instrumented to collect performance data, and then the assertions are checked automatically against the data to detect violations signifying potential performance bugs.

Proceedings of the 1992 MIT Student Workshop on VLSI and Parallel Systems

2023-03-30T03:26:29Z

Proceedings of the 1992 MIT Student Workshop on VLSI and Parallel Systems Leiserson, C.E. Proceedings of the 1992 MIT Student Workshop on VLSI and Parallel Systems. The papers in this volume were submitted to the 1992 MIT Student Workshop on VLSI and Parallel Systems. The workshop was organized by the VLSI and Parallel Systems Group at MIT to promote an interchange of ideas among the various research activities at MIT in VSLI and parallel systems. It was held on July 21, 1992 at the MIT Endicott House in Dedham, Massachusetts. Of 54 papers in this proceedings, 16 were chosen for presentation at the workshop. These papers are marked with an asterisk.

Video Coding and the Application Level Framing Protocol Architecture

2023-03-30T04:24:56Z

Video Coding and the Application Level Framing Protocol Architecture Heybey, Andrew T. As networks and computers become faster, real time video transmission is expected to become common. Variable bit rate video coders will be used in order to take advantage of the statistical multiplexing gain and bandwidth efficiency of packet switched networks.

PIPES: Linguistic Support for Ordered Asynchronous Invocations

2023-03-30T04:07:35Z

PIPES: Linguistic Support for Ordered Asynchronous Invocations Colbrook, Adrian; Brewer, Eric A.; Hsieh, Wilson C.; Wang, Paul; Weihl, William E. We describe pipes, a new linguistic mechanism for sequences of ordered asynchronous procedure calls in multiprocessor systems. Pipes allow a sequence of remote invocations to be performed in order, but asynchronously with respect to the calling thread.

Organization of Systems with Bussed Interconnections

2023-03-30T04:27:14Z

Organization of Systems with Bussed Interconnections Kipnis, Shlomo This thesis explores using busses in communication architectures and control structures. First, we investigate the organization of permutation architectures with bussed interconnections. We explore how to efficiently permute data among VLSI chips in accordance with a predetermined set of permutations.

Algorithms for Exploring an Unknown Graph

2023-03-30T04:21:16Z

Algorithms for Exploring an Unknown Graph Betke, Margrit We consider the problem of exploring an unknown strongly connected directed graph. We use the exploration model introduced by Deng and Papadimitriou [DP90]. An explorer follows the edges of an unknown graph until she has seen all the edges and vertices of the graph.

On the Sample Complexity of PAC-learning using Random and Chosen Examples

2023-03-30T04:25:20Z

On the Sample Complexity of PAC-learning using Random and Chosen Examples Eisenberg, Bronwyn Bonnie Two protocols used for learning under the pac-learning model introduced by Valiant are learning from random examples and learning from memberships queries. Membership queries have been used to efficiently and exactly learn a concept class C that is too difficult to pac-learn using random examples.

Modeling Speaker Variability and Imposing Speaker Constrainst in Phonetic Classification

2023-03-30T03:01:46Z

Modeling Speaker Variability and Imposing Speaker Constrainst in Phonetic Classification Niyogi, Partha This thesis deals with intra-speaker correlation analyses of speech sounds, and the possible utilization of this correlation to speech recognition. Current approaches to phonetic classification, regardless of whether they use context-dependent or -independent models, achieve classification based on locally optimum criteria.

A Distributed Data-balanced Dictionary Based on the B-link tree

2023-03-30T03:59:01Z

A Distributed Data-balanced Dictionary Based on the B-link tree Johnson, Theodore; Colbrook, Adrian Many concurrent dictionary data structures have been proposed, but usually in the context of shared memory multiprocessors. In this paper, we present an algorithm for a concurrent distributed B-tree that can be implemented on message passing paralle

The Design and Implementation of a Parallel Persistent Object System

2023-03-30T03:06:30Z

The Design and Implementation of a Parallel Persistent Object System Heytens, Michael L. This report describes Anga, an experimental persistent object system that we have developed that utilizes parallelism in a fundamental way to enhance performance. Parallelism is incorporated into the design of the system at all levels. We begin wit

File Systems with Multiple File Implementations

2023-03-30T03:18:10Z

File Systems with Multiple File Implementations Stata, Raymie This thesis proposes ideas for designing file system software for the large, high-performance file server hardware we feel will be common in the middle to late nineties. In particular, the thesis examines the value and pragmatics of file systems wit

Preventing Recursion Deadlock in Concurrent Object-oriented Systems

2023-03-30T03:53:03Z

Preventing Recursion Deadlock in Concurrent Object-oriented Systems Brewer, Eric A.; Waldspurger, Carl A. This paper presents solutions to the problem of deadlock due to recursion in concurrent object-oriented programming languages. Two language-independent, system-level mechanisms for solving this problem are proposed: a novel technique using multi-ported objects, and a named-threads scheme that borrows from previous work in distributed computing. We compare the solutions and present an analysis of their relative merits.

Full Abstraction and the Context Lemma 1

2023-03-30T03:42:57Z

Full Abstraction and the Context Lemma 1 Jim, Trevor; Meyer, Albert R. It is impossible to add a combinator to PCF to achieve full abstraction for models such as Berry's stable domains in a way analogous to the addition of the "parallel-or" combinator that achieves full abstraction for the familiar cpo model.

Scalable Reader-writer Locks for Parallel Systems

2023-03-30T04:18:11Z

Scalable Reader-writer Locks for Parallel Systems Hsieh, William C.; Weihl, William E. Current algorithms for reader-writer synchronization exhibit poor scalability because they do not allow readers to acquire locks independently. We describe two new algorithms for reader-writer synchronization that allow parallelism among readers during lock acquisition.

PRELUDE: A System for Portable Parallel Software

2023-03-30T03:01:11Z

PRELUDE: A System for Portable Parallel Software Weihl, William Edward; Brewer, Eric A.; Colbrook, Adrian; Dellarocas, Chrysanthos N.; Hsieh, Wilson; Joseph, Anthony; Waldspurger, Carl; Wang, Paul This paper describes PRELUDE, a programming language and accompanying system support for writing portable MIMD parallel programs. PRELUDE supports a methodology for designing and organizing parallel programs that makes them easier to tune for particular architectures and to port to new architectures.

The Real-time Cost of Timing Uncertainty: Consensus and Failure Detection

2023-03-30T04:26:18Z

The Real-time Cost of Timing Uncertainty: Consensus and Failure Detection Ponzio, Stephen J. In real distributed systems, processes may have only inexact information about the amount of real time needed for primitive operations such as process steps. This thesis studies the effect of this timing uncertainty on the real-time behavior of distributed systems.

Algorithms for Search Trees on Message-passing Architectures

2023-03-30T03:34:58Z

Algorithms for Search Trees on Message-passing Architectures Colbrook, Adrian; Brewer, Eric A.; Dellarocas, Chrysanthos N.; Weihl, William E. In this paper we describe a new algorithm for maintaining a balanced search tree on a message-passing MIMD architecture; the algorithm is particularly well suited for implementation on a small number of processors.

Proteus: A High-performance Parallel-architecture Simulator

2023-03-30T04:03:22Z

Proteus: A High-performance Parallel-architecture Simulator Brewer, Eric A.; Dellarocas, Chrysanthos N.; Colbrook, Adrian; Weihl, William E. PROTEUS is a high-performance simulator for MIMD multiprocessors. It is fast, accurate, and flexible: it is one to two orders of magnitude faster than comparable simulators, it can reproduce results from real multiprocessors, and it is easily configured to simulate a wide range of architectures.

The Use of Distinctive Features for Automatic Speech Recognition

2023-03-30T04:16:51Z

The Use of Distinctive Features for Automatic Speech Recognition Meng, Helen Mei-Ling One of the most critical and yet unsolved problems in phonetic recognition is the transformation of the continuous speech signal to a discrete representation for accessing words in the lexicon. In order to find an efficient description of speech for recognition tasks, our research investigates to use distinctive features.

Secure Computation (Preliminary Report)

2023-03-30T04:14:18Z

Secure Computation (Preliminary Report) Micali, Silvio; Rogaway, Phillip We define what it means for a network of communicating players to securely compute a function of privately held inputs. Intuitively, we wish to correctly compute its value in a computer manner which protects the privacy of each player's contribution, even though a powerful adversary may endeavor to disrupt this enterprise.

An Information-theoretical Approach to Studying Phoneme Collocational Constrainst

2023-03-30T03:57:11Z

An Information-theoretical Approach to Studying Phoneme Collocational Constrainst Kassel, Robert Howard This thesis describe a lexical study of phoneme collocational constraints using a metric motivated by information theory. Phonologists have been describing the permissible combination of phonemes in the form of phonotactic rules. They have shown that these rules often can be expressed in terms of phoneme equivalence classes.

Algorithms for Approximate Graph Coloring

2023-03-30T03:01:43Z

Algorithms for Approximate Graph Coloring Blum, Avrim

A High-performance Retargetable Simulator for Parallel Architectures

2023-03-30T03:21:25Z

A High-performance Retargetable Simulator for Parallel Architectures Dellarocas, Chrysanthos N. The complexity of the interaction between software and hardware in MIMD machines makes experimental evaluation of parallel programs an import complement to theoretical analysis. Traditional techniques used to monitor the direct execution of programs are intrusive an d may lead to inaccurate results when applied to parallel programs.

Knowledge Representation for Supporting Decision Model Formulation in Medicine

2023-03-30T03:07:22Z

Knowledge Representation for Supporting Decision Model Formulation in Medicine Leong, Tze-Yun Clinical decision making involves a large, complex, and ever-changing body of knowledge. Characterizing such knowledge illuminates the representational and computational requirements for automated clinical decision analysis.

The Round Complexity of Secure Protocols

2023-03-30T03:11:39Z

The Round Complexity of Secure Protocols Rogaway, Phillip Assume we have a network of three of more players, each player in possession of some private input. The players want to compute some function of these private inputs, but in a way which protects the privacy of each participant's contribution.

Performance Tradeoffs in Multithreaded Processors

2023-03-30T03:51:49Z

Performance Tradeoffs in Multithreaded Processors Agarwal, Anant High network latencies in large-scale multiprocessors can cause a significant drop in processor utilization. By maintaining multiple process contexts in hardware and switching among them in a few cycles, multithreaded processors can overlap computation with memory accesses and reduce processor idle time.

Randomness and Robustness in Hypercube Computation

2023-03-30T03:27:14Z

Randomness and Robustness in Hypercube Computation Newman, Mark Joseph In this thesis we explore means by which hypercubes can compute despite faulty processors and links. We also study techniques which enable hypercubes to simulate dynamically changing networks and data structures.

Waiting Algorithms for Synchornization in Large-scale Multiprocessors

2023-03-30T04:05:53Z

Waiting Algorithms for Synchornization in Large-scale Multiprocessors Lim, Beng-Hong; Agarwal, Anant Through analysis and experiments, this paper investigates two-phase waiting algorithms to minimize the cost of waiting for synchronization in large-scale multiprocessors. In a two-phase algorithm, a thread first waits by polling a synchronization variable.

An Evaluation of Concurrent Priority Queue Algorithms

2023-03-30T04:15:58Z

An Evaluation of Concurrent Priority Queue Algorithms Huang, Qin The priority queue is a fundamental data structure that is used in a large variety of parallel algorithms, such as multiprocessor scheduling and parallel best-first search of state-space graphs.

The Spectral Norm of Finite Functions

2023-03-30T03:20:46Z

The Spectral Norm of Finite Functions Bellare, Mihir In many recent results in learning and computational complexity theory which rely on Fourier analysis, the spectral norm plays a key role. An understanding of this quantity would appear to be useful in both gauging and exploiting these results, and in understanding the underlying techniques.

TCP Packet Trace Analysis

2023-03-30T04:26:30Z

TCP Packet Trace Analysis Shepard, Timothy Jason Examination of a trace of packets collected from the network is often the only method available for diagnosing protocol performance problems in computer networks. This thesis explores the use of packet traces to diagnose performance problems of the transport protocol TCP.

Cache Coherence Protocols for Large-Scale Multiprocessors

2023-03-30T04:13:00Z

Cache Coherence Protocols for Large-Scale Multiprocessors Chaiken, David Lars Caches have the potential to provide multiprocessors with an automatic mechanism for reducing both network traffic and average memory access latency. However, cache-based systems must address the problem of cache coherence.

An Incremental Type Inference System for the Programming Language ID

2023-03-30T03:55:31Z

An Incremental Type Inference System for the Programming Language ID Gupta, Shail Aditya Modern computing environments strive to be robust and reliable, and at the same time, aim at providing enough flexibility to an interactive user to edit, debug, and test programs easily and efficiently.

Specification and Verification of Real-team Constraints in Coarse-grain Dataflow

2023-03-30T03:32:58Z

Specification and Verification of Real-team Constraints in Coarse-grain Dataflow Henry, Dana S. We present a method for verifying real-time constraints in a distributed, coarse-grain dataflow environment starting with a program which has already been allocated onto a machine. The user specifies the timing of each module together with real-time constraints; and we verify the constraints.

On Retiming Synchronous Circuitry and Mixed-integer Optimization

2023-03-30T03:29:14Z

On Retiming Synchronous Circuitry and Mixed-integer Optimization Papaefthymiou, Marios Christos In this paper we investigate properties of retiming, a circuit transformation which preserves the behavior of the circuit as a whole. We present an algorithm which transforms a given combinational circuit into a functionally equivalent pipelined circuit with minimum latency and clock-period no greater than a given upper bound c.

Lazy Replication: Exploiting the Semantics of Distributed Services

2023-03-30T04:13:39Z

Lazy Replication: Exploiting the Semantics of Distributed Services Ladin, Rivka; Liskov, Barbara; Shrira, Liuba; Ghemawat, Sanjay To provide high availability for services such as mail or bulletin boards, data must be replicated. One way to guarantee consistency of replicated data is to force service operations to occur in the same order at all sites, but this approach is expensive.

Design and Implementation of a Packet Switched Routing Chip

2023-03-30T04:18:13Z

Design and Implementation of a Packet Switched Routing Chip Joerg, Christopher Frank Monsoon is a parallel processing dataflow computer that will require a high bandwidth interconnection network. A packet switched routing chip (PaRC) is described that will be used as the basis of this network. PaRC is a 4 by 4 routing switch which has been designed and fabricated as a CMOS gate array.

On the Complexity of Computing Algebraic Functions

2023-03-30T04:18:27Z

On the Complexity of Computing Algebraic Functions Mansour, Yishay This research addresses the problem of proving lower bounds on the complexity of algebraic computations involving the floor operation. The model of computation considered is a computation tree with the set of basic operations {+,-,*,*,[.],._ }. The constants available to the computation are 0 and 1, and every other constant needs to be generated explicitly.

Analysis of the Held-Karp Heuristic for the Traveling Salesman Problem

2023-03-30T04:16:12Z

Analysis of the Held-Karp Heuristic for the Traveling Salesman Problem Williamson, D.P. The Held-Karp heuristic for the Traveling Salesman Problem (TSP) has in practice provided near-optimal lower bounds on the cost of solutions to the TSP. We analyze the structure of Held-Karp solutions in order to shed light on their quality.

Efficient At-most-once Messages Based on Synchronized Clocks

2023-03-30T03:38:16Z

Efficient At-most-once Messages Based on Synchronized Clocks Liskov, Barbara; Shrira, Liuba; Wroclawski, John This paper describes a new message passing protocol that provides guaranteed detection of duplicate messages even when the receiver has no state stored for the sender.

Disconnected Actions: An Asynchronous Extensions to a Nested Atomic Action System

2023-03-30T03:47:39Z

Disconnected Actions: An Asynchronous Extensions to a Nested Atomic Action System Ben-Zvi, Boaz Nested transactions, a generalization of atomic transactions, provide a uniform mechanism for coping with failures and obtaining concurrency within an action.

Automatic Replication for Highly Available Services

2023-03-30T03:48:02Z

Automatic Replication for Highly Available Services Ghemawat, Sanjay Replicating various components of a system is a common technique for providing highly available services in the presence of failures. A replication scheme is a mechanism for organizing these replicas so that as a group they provide a service that has the same semantics as the original unreplicated service. Viewstamped replication is a new replication scheme for providing high availability.

Rate-based Congestion Control in Networks with Smart Links

2023-03-30T04:07:22Z

Rate-based Congestion Control in Networks with Smart Links Heybey, Andrew Tyrrell I use a network simulator to explore rate-based congestion control in networks with "smart" links that can feed back information to tell senders to adjust their transmission rates. This method differs in a very important way from congestion control in

ML with Extended Pattern Matching and Subtypes

2023-03-30T03:04:40Z

ML with Extended Pattern Matching and Subtypes Jategaonkar, Lalita A. We extend a fragment of the programming language ML by incorporating a more general form of record pattern matching and providing for user-declared subtypes. Together, these two enhancements may be used to support a restricted object-oriented program

Probabilistic Reasoning in the Domain of Genetic Counseling

2023-03-30T04:08:52Z

Probabilistic Reasoning in the Domain of Genetic Counseling Harris, Nomi L. This paper describes a program, GENINFER, which uses belief networks to calculate risks of inheriting genetic disorders. GENINFER is based on Judea Pearl's [17] algorithm for fusion and propagation in probabilistic belief networks. These networks allow the effects of various pieces of information to be propagated and fused in such a way that, when equilibrium is reached, each proposition can be assigned a degree of believe consistent with the axioms of probability theory.

Should a Function Continue?

2023-03-30T03:42:16Z

Should a Function Continue? Riecke, Jon Gary We show that two l-calculus terms can be observationally congruent (i.e., agree in all contexts) but their continuation-passing transforms may not be. We also show that two terms may be congruent in all untyped contexts but fail to be congruent in a language with call/ cc operators, and that two terms may have the same meaning in a direct semantics but in a continuation semantics.

Typechecking is Undecidable when 'Type' is a Type

2023-03-30T03:42:17Z

Typechecking is Undecidable when 'Type' is a Type Reinhold, Mark B. A function has a dependent type when the type of its result depends upon the value of its argument. The type of all types is the type of every type, including itself. In a typed l-calculus, these two features synergize in a conceptually clean and uniform way to yield enormous expressive power at very little apparent cost. By reconstructing and analyzing a paradox due to Girard, we argue that there is no effective typechecking algorithm for such a language.

Using Cycles and Scaling in Parallel Algorithms

2023-03-30T03:58:35Z

Using Cycles and Scaling in Parallel Algorithms Stein, Clifford We introduce the technique of decomposing an undirected graph by finding a maximal set of edge-disjoint cycles. We give a parallel algorithm to find this decomposition in O(log n) time on (m+ n)/log n processors. We then use this decomposition to to give the first efficient parallel algorithm for finding an approximation to a minimum cycle cover.

ParaTran: A Transparent, Transaction Based Runtime Mechanism for Parallel Execution of Scheme

2023-03-30T03:20:02Z

ParaTran: A Transparent, Transaction Based Runtime Mechanism for Parallel Execution of Scheme Katz, Morry The number of applications requiring high speed symbolic computation and the performance requirements of these projects are both rapidly increasing. However, the computer science community's ability to produce high performance uniprocessor hardware is being outstripped by these needs. Therefore, we propose a unique multiprocessing solution to the high speed, symbolic computation problem. Our approach is to develop a transparent runtime mechanism for executing standard, sequential Lisp code on a multiprocessor computer.

Optimistic Concurrency Control for Nested Distributed Transactions

2023-03-30T04:08:58Z

Optimistic Concurrency Control for Nested Distributed Transactions Gruber, Robert Edward Optimistic concurrency control techniques allow atomic transactions (or actions for short) to execute without synchronization, relying on commit-time validation to ensure serializability. Previous work in this area has focussed on single-level actions. This thesis extends previous work on optimistic concurrency control to distributed system with nested actions.

A Study of Backoff Barrier Synchronization

2023-03-30T04:11:55Z

A Study of Backoff Barrier Synchronization Cherian, Mathews Malieakkal Shared-memory multiprocessors commonly use shared variables for synchronization. Simulations of real parallel applications show that large-scale cache-coherent multiprocessors suffer significant amounts of invalidation traffic due to synchronization. Large multiprocessors that do not cache synchronization variables are often more severely impacted.

Network Layer Protocols with Byzantine Robustness

2023-03-30T03:47:17Z

Network Layer Protocols with Byzantine Robustness Perlman, Radia The Network Layer of a network architecture is a distributed protocol that facilitates packet delivery across multiple hops. One of its chief functions is the calculation of routes throughout the network. Traditional Network Layer protocols have addressed robustness in the face of simple failures, i.e. nodes or links becoming inoperative. This thesis examines Network Layer protocol designs that are robust in the presence in the Byzantine failures, i.e., nodes that through malice or malfunction exhibit arbitrary behavior such as corrupting, forging, or delaying routing protocol messages.

Code-mapping Policies for the Tagged-token Dataflow Architecture

2023-03-30T03:46:19Z

Code-mapping Policies for the Tagged-token Dataflow Architecture Maa, Gino K. Multiprocessing seems to be the only viable way to gain significant speedup beyond that afforded by performance advances in semiconductor devices and hardware construction, which are beginning to face the limitations of physics. Although it is relatively easy to improve the "raw" computational performance of a system simply by adding more processors to it, the far more difficult task is to insure that the additional resources actually reduce a program's computing time.

A Fault-tolerant Network Kernel for Linda

2023-03-30T03:49:20Z

A Fault-tolerant Network Kernel for Linda Xu, Andrew S. The parallel programming system Linda consists of a number of processes and a shared memory called the tuple space. In a distributed implementation of Linda, processes and the tuple space reside on different computing nodes connected by a communications network subject to a variety of node and network failures.

Viewstamped Replication for Highly Available Distributed Systems

2023-03-30T03:19:22Z

Viewstamped Replication for Highly Available Distributed Systems Oki, Brian Masao This dissertation presents viewstamped replication, a new algorithm for the implementation of highly available computer services that continue to be usable in spite of node crashes and network partitions. Our goal is to design an efficient mechanism that makes it easy for programmers to implement these services without complicating the programming model.

FX-87 Performance Measurements: Dataflow Implementation

2023-03-30T04:16:53Z

FX-87 Performance Measurements: Dataflow Implementation Hammel, R. Todd; Gifford, David K. We analyze how much the FX-87 static effect system can improve the execution times of five benchmark programs on a parallel graph interpreter. Three of our benchmark programs do not use side-effects (factorial, fibonacci, and polynomial division) an

Compsoing Data & Process Descriptions in the Design of Software Systems

2023-03-30T03:01:31Z

Compsoing Data & Process Descriptions in the Design of Software Systems Jackson, Daniel Two paradigms are dominant in software development, the data paradigm and the process paradigm. Our contention is that relying exclusively on either is counter-productive. In the data paradigm, a system is specified as operations acting on states. The process paradigm focuses on sequences of events.

Automatic Qualitative Analysis of Ordinary Differential Equations Using Piecewise Linear Approximations

2023-03-30T04:12:55Z

Automatic Qualitative Analysis of Ordinary Differential Equations Using Piecewise Linear Approximations Sacks, Elisha, Peretz This thesis explores automating the qualitative analysis of physical systems. Scientists and engineers model many physical systems with ordinary differential equations. They deduce the behavior of the system by analyzing the equations. Most realistic models are nonlinear, hence difficult or impossible to solve explicitly.

A High-level Signal Processing Programming Language

2023-03-30T03:13:15Z

A High-level Signal Processing Programming Language Hicks, James Edward, Jr. The motivations for an abstract, diagrammatic signal processing language are presented along with a study of the semantics that such language should have. D-PICT, the proposed Digital Signal Processing Pictorial Language, is thoroughly described. D-PICT has a diagrammatic representation with a corresponding textual representation.

Diversity-based Inference of Finite Automata

2023-03-30T04:19:11Z

Diversity-based Inference of Finite Automata Schapire, Robert Elias We present a new procedure for inferring the structure of a finite-state automaton (FSA) from its input/output behavior, using access to the automaton to perform experiments. Our procedure uses a new representation for FSA's, based on the notion of equivalence between tests.

Constructing a Highly-available Location Service for a Distributed Environment

2023-03-30T03:31:44Z

Constructing a Highly-available Location Service for a Distributed Environment Jing-Hwa Hwang, Deborah One possible advantage a distributed system has over a centralized system is the ability to move objects from one node to another. For example, we may want to move an object if the node where it resides is overloaded. This thesis proposes to use a location service to aid in finding objects that move.

A Technique for Constructing Highly-Available Services

2023-03-30T03:33:44Z

A Technique for Constructing Highly-Available Services Ladin, Rivka; Liskov, Barbara; Shrira, Liuba This paper describes a general method for constructing a highly available service for use in a distributed system. It gives a specific implementation of the method and proves the implementation correct. The service consists of replicas that reside at several different locations in a network. It presents its clients with a consistent view of its state, but the view may contain old information.

CALVIN: A Rule Based Expert System for Improving Arrhymia Detector Performance During Noisy ECGS

2023-03-30T04:02:14Z

CALVIN: A Rule Based Expert System for Improving Arrhymia Detector Performance During Noisy ECGS Muldrow, Warren K. Human experts far outperform automated arrhythmia detectors in analyzing ECG data corrupted by noise and artifact. Humans make use of considerable a priori knowledge about cardiac electrophysiology and knowledge acquired from the specific ECG under analysis. R-R interval, coupling intervals of ectopic beats, and commonly occurring beat patterns observed during noise-free ECG segments form a knowledge base which is used in accurately detecting and classifying true QRS complexes in the presence of severe noise.

A Framework for Incorporating Abstraction Mechanisms into the Logic Programming Paradigm

2023-03-30T03:37:05Z

A Framework for Incorporating Abstraction Mechanisms into the Logic Programming Paradigm Zachary, Joseph Lawrence To help make logic programming more suitable for writing large systems, we develop linguistic mechanisms that permit the organization of logic programs around abstractions. In particular, we present the design of Danali, an equational logic programming language that supports predicate and data abstraction.

Rule Based Analysis of Computer Security

2023-03-30T04:04:55Z

Rule Based Analysis of Computer Security Baldwin, Robert W. Computers are rarely as secure as they could be. Users are lax or inconsistent in the way they configure a computer's protection system, and these user mistakes often lead to serious security holes. For example, a privileged user might accidentally make his login initialization file publicly writable and that mistake could allow ordinary users to acquire super-user privileges.

Argus Reference Manual

2023-03-30T03:37:32Z

Argus Reference Manual Liskov, Barbara; Day, M.; Herlihy, M.; Johnson, P.; Leavens, G. Argus is an experimental language/system designed to support the construction and execution of distributed programs. Argus is intended to support only a subset of the applications that could benefit from being implemented by a distributed program. Two properties distinguish these applications: they make use of on-line data that must remain consistent in spite of concurrency and hardware failures, and they provide services under real-time constraints that are not severe.

Walter User's Manual (Version 1.0)

2023-03-30T03:19:54Z

Walter User's Manual (Version 1.0) Gifford, David K.; Cote, Robert G.; Segal, David A. Walter is a UNIX program that provides access to databases located at MIT via the DARPA Internet. The databases provided by Walter include the full-text of the New York Times for the past 90 days. A sophisticated full-text query language is provided, and Walter uses a query routing algorithm to direct requests to the proper database server at MIT.

Clipping Service User's Manual (Version 1.2)

2023-03-30T03:20:36Z

Clipping Service User's Manual (Version 1.2) Gifford, David K.; Cote, Robert G.; Segal, David A. The Clipping Service is a program that will send selected stories from the New York Times and other information sources to you via electronic mail. In order to use the Clipping Service, you first describe your interests to the Clipping Service in a simple full-text query language, and then mail this interest profile to the DARPA Internet mail address clip@db.lcs.mit.edu.

Boston Community Information System - 1986 Experimental Test Results

2023-03-30T03:49:07Z

Boston Community Information System - 1986 Experimental Test Results Gifford, David K.; Heitmann, Dawn; Segal, David A.; Cote, Robert G.; Tanacea, Kendra; Burmaster, David E. This report describes the first year of an experimental test of the Boston Community Information System (Boston CommInS). The experiment implements new ideas of data communication and database design in the transmission and reception of data. The system offers the Associated Press and New York Times to participants and is provided in exchange for their monthly feedback.

KOLA: Knowledge Organization Language

2023-03-30T04:11:33Z

KOLA: Knowledge Organization Language Jang, Yeona The focus of this research is on a representation of knowledge that captures the structure of a domain into the computational model for efficient retrieval and reasoning. With this desideratum in mind, a concept-based knowledge representation system KOLA (Knowledge Organization LAnguage ) is described.

Communication Patterns in a Symbolic Multiprocessor

2023-03-30T03:58:45Z

Communication Patterns in a Symbolic Multiprocessor Nuth, Peter Robert An important design decision for large scale multiprocessors is the balance of processor power to communication network bandwidth. In order to evaluate different design alternatives, it is necessary to be able to predict the load imposed on the network by a programming model. This thesis quantifies that communication load for a model of parallel symbolic computing using the Multilisp language.

Dynamic Programming on Graphs with Bounded Treewidth

2023-03-30T03:21:15Z

Dynamic Programming on Graphs with Bounded Treewidth Bodlaender, Hans L. In this paper we study the complexity of graph decision problems, restricted to the class of graphs with treewidth k, (or equivalently, the class of partial k-trees), for fixed k. We introduce two classes of graph decision problems, LCC and ECC, and subclasses C-LCC, and C-ECC. We show that each problem in LCC (or C-LCC) is solvable in polynomial (O(nc)) time, when restricted to graphs with fixed up-perbounds on the treewidth and degree; and that each problem in ECC (or C- ECC) is solvable in polynomial (O(n c)) time, when restricted to graphs with a fixed upperbound on the treewidth (with given corresponding tree-decomposition).

Synthesis of Self-timed VLSI Circuits from Graph-theoretic Specifications

2023-03-30T03:52:00Z

Synthesis of Self-timed VLSI Circuits from Graph-theoretic Specifications Chu, Tam-Anh This thesis presents an approach for direct and efficient synthesis of self-timed (asynchronous) control circuits from formal specifications called Signal Transition Graphs (STGs). Control circuits synthesized from this graph model are speed-independent and capable of performing concurrent operation.

MAM: A Semi-automatic Debugging Tool for Distrubuted Programs

2023-03-30T04:18:54Z

MAM: A Semi-automatic Debugging Tool for Distrubuted Programs Kolodney, Lawrence Kenneth Traditional debuggers, designed to examine single process serial programs, do not provide sufficient functionality for efficient debugging of distributed programs. There are a number of fundamental differences in the way in which a programmer understands the execution of a distributed programs, and a debugger must present data to its user in light of that fact.

Efficient Methods for Calculating Maximum Entropy Distributions

2023-03-30T03:35:22Z

Efficient Methods for Calculating Maximum Entropy Distributions Goldman, Sally A. We present a new algorithm for computing the maximum entropy probability distribution satisfying a set of constraints. Unlike previous approaches, our method is integrated with the planning of data collection and tabulation. We show how adding constraints and performing the associated additional tabulations can substantially speed up computation by replacing the usual iterative techniques with a straight-forward computation.

Data Replication in Nested Transaction Systems

2023-03-30T04:03:32Z

Data Replication in Nested Transaction Systems Goldman, Kenneth J. Gifford's basic Quorum Consensus algorithm for data replication is generalized to accommodate nested transactions and transaction failures (aborts). A formal description of the generalized algorithm is presented using the new Lynch-Merritt input-output automaton model for nested transaction systems.

Temporal Reasoning in Medical Expert Systems

2023-03-30T03:03:47Z

Temporal Reasoning in Medical Expert Systems Kohane, Isaac S. Diseases develop and change over time. Much of the distinction between pathophysiological complexes rests on the temporal relations of their component events. Therefore, knowledge bases that fail to capture the temporal component of the course of disease omit useful diagnostic knowledge.

An Expert System for Diagnosing Gait for Cerebral Palsy Patients

2023-03-30T03:51:13Z

An Expert System for Diagnosing Gait for Cerebral Palsy Patients Hirsch, David Edward Many first generation expert systems in medicine assumed that a single fault was the cause of the patient's problems. However, this is not always so and in the domain of gait analysis this is usually not the case. This work looks at an expert system for performing gait analysis on cerebral palsy patients. The system is able to handle cases where there are many interacting faults causing the patient's gait deviations.

Hierarchical Correctness Proofs for Distributed Algorithms

2023-03-30T04:22:52Z

Hierarchical Correctness Proofs for Distributed Algorithms Lynch, Nancy A.; Tuttle, Mark S. This thesis introduces a new model for distributed computation in asynchronous networks, the input-output automaton. This simple, powerful model captures in a novel way the game-theoretical interaction between a system and its environment, and allows fundamental properties of distributed computation such as fair computation to be naturally expressed.

A Simulation Environment for Schema

2023-03-30T03:04:35Z

A Simulation Environment for Schema St.Pierre, Margaret Ann In present day circuit design, many independent simulation tools are available for analyzing circuits at various levels of detail. This thesis presents a framework to tie these tools into the Simulation Environment in Schema, an integrated CAD system. The framework easily incorporates additional simulators, serves as a foundation upon which to build new analysis tools, and provides the ability for mixed-mode simulation.

Data Flow Computer Architecture Final Report

2023-03-30T03:01:21Z

Data Flow Computer Architecture Final Report Dennis, Jack B. This report covers the work done by Computation Structures Group of the MIT Laboratory for Computer Science on developing models, languages, and architectures for data flow computation from 1966 to the end 1985. The work was supported by research grants and contracts from NSF, the University of California, DOE, NASA, and DARPA having periods of support as follows: Advanced Research Projects Agency (DARPA).

Remote Pipe and Procedures for Efficient Distributed Communication

2023-03-30T04:03:55Z

Remote Pipe and Procedures for Efficient Distributed Communication Gifford, D. A new communication model for distributed systems is described that combines the advantages of remote procedure call with the efficient transfer of bulk data. Three ideas form the basis of this model. First, remote procedures are first-class values which can be freely exchanged among nodes, thus enabling a greater variety of protocols to be directly implemented in a remote procedure call framework.

Congestion Control in Routing Networks

2023-03-30T03:53:01Z

Congestion Control in Routing Networks Chien, Andrew Andai Multistage routing networks present an attractive cost-effective method of interconnection for medium to large scale multiprocessors. Recent results concerning performance degradation in the presence of "hot spots" have raised serious questions about the robustness of previous performance estimates for these routing networks. Research to date has focused on a limited class of hot spots-those in which all the hot spot traffic is destined for the same memory address.

Logic Simulation of a Multiprocessor

2023-03-30T03:47:26Z

Logic Simulation of a Multiprocessor Bradley, Elizabeth The performance of circuit simulators running on SISD computers is fundamentally limited by the Von Neumann bottleneck. Multiprocessors do not share this limitation. The task of solving the equations for the many parallel signal paths found in most circuits lends itself readily to concurrent computation. for both of these reasons, parallel processing is a highly promising approach to circuit simulation. This thesis explores several facets of this problem.

The Notion of Security for Probabilistic Public-key Cryptosystems

2023-03-30T03:04:08Z

The Notion of Security for Probabilistic Public-key Cryptosystems Sloan, Robert Hal The purpose of a cryptosystem is to allow people to communicate securely over an open channel. Before one can discuss whether a cryptosystem meets this goal, however, one must first rigorously define what is meant by security. Three very different formal definitions of security for public-key cryptosystems have been proposed-two by Goldwasser and Micali and one by Yao. In this thesis, it is shown that the three definitions are essentially equivalent.

MACE: A Multiprocessing Approach to Circuit Extraction

2023-03-30T04:00:32Z

MACE: A Multiprocessing Approach to Circuit Extraction Levitin, Samuel M.; Terman, Christopher J.; Slater, Kenneth H. The ever-increasing complexity of VLSI chips threaten to choke out all available computer power unless methods are devised to keep the CAD tasks conveniently sized. A review of the current methods of multiprocessing approaches in the domain of layout verification precedes the discussion of current work.

Long Atomic Computations

2023-03-30T04:05:09Z

Long Atomic Computations Ng, Pui Distributed computing systems are becoming commonplace and offer interesting opportunities for new applications. In a practical system, the problems of synchronizing concurrent computations and recovering from failures must be dealt with effectively.

Replication and Reconfiguration in a Distributed Mail Repository

2023-03-30T04:00:47Z

Replication and Reconfiguration in a Distributed Mail Repository Day, Mark S. Conventional approaches to programming produce centralized programs that run on a single computer. However, an unconventional approach can take advantage of low-cost communication and small, inexpensive computers. A distributed program provides service through programs executing at several nodes of a distributed system.

Efficient Graph Algorithms for Sequential and Parallel Computers

2023-03-30T03:21:27Z

Efficient Graph Algorithms for Sequential and Parallel Computers Goldberg, Andrew V.

Boston Community Information System User's Manual

2023-03-30T03:38:35Z

Boston Community Information System User's Manual Segal, David A.; Gifford, David K.; Lucassen, John M.; Henderson, James B.; Berlin, Stephen T.; Burmaster, David E. The Boston Community Information System turns your computer into a personal information assistant that monitors the news as it happens. This experiment, CommInS, tests a new way of distributing world news as it happens and features from the New York Times and the Associate Press wire service directly to personal computers via radio waves.

Compaction with Automatic Job Introduction

2023-03-30T04:09:30Z

Compaction with Automatic Job Introduction Maley, F. Miller This thesis presents an algorithm for one-dimensional compaction of VLSI layouts. It differs from older methods in treating wires not as objects to be moved, but as constraints on the positions of other circuit components. These constraints are determined for each wiring layer using the theory of planar routing.

A Compiler for the MIT Tagged-token Dataflow Architecture

2023-03-30T03:36:57Z

A Compiler for the MIT Tagged-token Dataflow Architecture Traub, Kenneth R. Compilation of the programming language Id Nouveau into machine code for the MIT tagged-token dataflow architecture is thoroughly described. Id Nouveau is a higher-order functional language augmented with a novel data structure facility known as I-Structures. The tagged-token dataflow architecture is a dataflow computer of the dynamic variety.

Programming Simultaneous Action Using Common Knowledge

2023-03-30T03:30:13Z

Programming Simultaneous Action Using Common Knowledge Moses, Yoram; Tuttle, Mark R. This work applies the theory of knowledge in distributed systems to the design of efficient fault-tolerant protocols. We define a large class of problems requiring coordinated, simultaneous action in synchronous systems, and give a method of transforming specifications of such problems into protocols that are optimal in all runs: for every possible input to the system and faculty processor behavior, these protocols are guaranteed to perform the simultaneous actions as soon as any other protocol could possibly perform them.

The X Window System

2023-03-30T04:11:32Z

The X Window System Scheifler, Robert W.; Gettys, Jim An overview of the X Window System is presented, focusing on the system substrate and the low-level facilities provided to build applications and to manage the desktop. The system provides high-performance, high-level, device-independent graphics.

Introduction to the Theory of Nested Transactions

2023-03-30T03:01:09Z

Introduction to the Theory of Nested Transactions Lynch, Nancy A.; Merritt, Michael A new formal model is presented for studying concurrency and resiliency properties for nested transactions. The model is used to state and prove correctness of a well-known locking algorithm.

The Clock Distribution Systems of the Multiprocessor Emulation Facility

2023-03-30T03:53:09Z

The Clock Distribution Systems of the Multiprocessor Emulation Facility Younis, Saed G. Consisting of 32 high-speed processors, the multiple processor emulation facility communicates data between its processors through the use of synchronous, high-bandwidth packet switches residing on the ports of every processor. Because of the synchronous nature of these packet switches, there was a need to design a clock distribution system that can distribute a clock signal to the 32 ports with as little clock skew as possible.

ID World: An Environment for the Development of a Dataflow Programs Written in ID

2023-03-30T03:25:43Z

ID World: An Environment for the Development of a Dataflow Programs Written in ID Morais, Dinarte R. The ID WORLD involves the interfacing of a compiler, interpreter, debugger and editor mode to create an environment for the development of dataflow programs written in ID. It replaces the Tagged-Token Dataflow Architecture (TTDA) Emulator as the foundation for Multiprocessor Emulation Facility at the Laboratory for Computer Science,M.I.T.

Correctness Conditions for Highly Available Replicated Databases

2023-03-30T03:40:06Z

Correctness Conditions for Highly Available Replicated Databases Lynch, Nancy A.; Blaustein, Barbara; Siegel, Michael Correctness conditions are given which describe some of the properties exhibited by highly available distributed database systems such as the SHARD (System for Highly Available Replicated Data) system currently being developed at Computer Corporation of America. This system allows a database application to continue operation in the face of communication failures, including network partitions.

Exploiting Parallelism in VLSI CAD

2023-03-30T03:44:22Z

Exploiting Parallelism in VLSI CAD Marantz, Joshua David In the domain of computer science, particularly VLSI CAD, an increasing amount of engineering time is spent running compute-bound programs. Many of these programs have an intrinsic parallelism that is externally accessible. This thesis describes a novel software system that uses a small number of independent computers connected by a network to exploit the parallelism inherent in existing software, and thereby, reduce its running time.

Simulating Applicative Architectures on the Connection Machine

2023-03-30T04:13:32Z

Simulating Applicative Architectures on the Connection Machine Kuszmaul, Bradley C. The Connection Machine (CM) is a highly parallel single instruction multiple data (SIMD) computer, which has been described as "a huge piece of hardware looking for a programming methodology.' Applicative languages, on the other hand, can be described as a programming methodology looking for a parallel computing engine.

Bounded Width Branching Programs

2023-03-30T03:46:03Z

Bounded Width Branching Programs Barrington, David A. We examine the branching program model of computation and in particular the classes of languages which can be recognized when the width of the programs is bounded by a constant. After slightly revising the framework of definitions to sharpen analogies with other models, we prove that width 5 polynomial size branching programs can recognize exactly the parallel complexity class NC1, refuting a conjecture of Borodin et al. in [BDFP83].

Intelligent Physiologic Modeling

2023-03-30T04:23:06Z

Intelligent Physiologic Modeling Kunstaetter, Robert This thesis describes the design and implementation of a knowledge based physiologic modeling systems (KBPMS) and a preliminary evaluation of its use as a learning resource within the context of an experimental medical curriculum--the Harvard New Pathway. KBPMS posesses combined numeric and qualitative simulation capabilities and provide explanations of its knowledge and behaviour.

A CATV-Based High-speed Packet-switching Network Design

2023-03-30T04:01:55Z

A CATV-Based High-speed Packet-switching Network Design Feldmeier, David Charles A high-speed packet-switching data network to the home can be built on an existing, unmodified, residential cable television (CATV) system. This thesis considers the theoretical and practical technical aspects of providing such a service and suggest a possible system design.

Primitives for Real-time Animation in Three Dimensions

2023-03-30T03:03:26Z

Primitives for Real-time Animation in Three Dimensions Chaing, Carol J. We present a general purpose imaging model which can efficiently produce computer-generated animated scenes. Displaying sophisticated graphics scenes is a computationally complex operation. Thus, an efficient imaging model is necessary for producing real-time motion.

Computation Management in a Single Address Space System

2023-03-30T03:47:21Z

Computation Management in a Single Address Space System Gibson, James C. A multiprogramming operating system needs a mechanism to recover from the termination of one of its computations. Cleaning up, or unlinking a terminated computation from those remaining requires identifying the end of a computation, freeing resources that the computation was using, and shutting down its interfaces with other computations.

Logical Structure for Functional Languages

2023-03-30T03:45:54Z

Logical Structure for Functional Languages Beckerle, Michael J. Functional Programming is frequently advocated as an appropriate programming discipline for parallel processing because of the difficulty of extracting parallelism from programs written in conventional sequential programming languages. Unfortunately, the use of Functional operations often implies excessive copying or unnecessary sequentiality in the access and construction of data structures.

Data Structure Management in a Data Flow Computer System

2023-03-30T03:40:25Z

Data Structure Management in a Data Flow Computer System Guharoy, Bhaskar VIM is an experimental computer system being developed at MIT for supporting functional programming. The execution mechanism of the computer is based on data flow. This thesis presents mechanisms for managing data structures in this system. This thesis also develops a methodology for designing computers, which is based on successive refinement of formal models of the computer.

Remote Evaluation

2023-03-30T04:12:33Z

Remote Evaluation Stamos, James William A new technique for computer-to-computer communication is presented that can increase the generality and performance of distributed systems. This technique, called Remote Evaluation, lets one computer send another computer a request in the form of a program. A computer that receives such a request executes the program in the request and returns the results to the sending computer.

Data Backup and Recovery in a Computer Architecture for Functional

2023-03-30T04:08:07Z

Data Backup and Recovery in a Computer Architecture for Functional Jagannathan, Suresh The Vim computer system, an experimental project under development in the MIT/LCS Computation Structures Group, is intended to examine the efficient implementation of functional languages using the principles of data flow computation. In this thesis, we examine how to incorporate backup and recovery mechanisms into this system to guarantee that no online information is lost because of hardware malfunction.

Boston Community Information System User Manual (Version 6.0)

2023-03-30T03:55:41Z

Boston Community Information System User Manual (Version 6.0) Lucassen, John M.; Gifford, David K.; Berlin, Stephen T.; Burmaster, David E. The Boston Community Information System turns your computer into a personal information assistant that monitors the news as it happens. This experiment, CommInS, tests a new way of distributing world news and features from the New York Times and the Associated Press (AP) wire service directly to personal computers via radio waves.

The Complexity of Graph Layour and Channel Routing for VLSI

2023-03-30T04:06:08Z

The Complexity of Graph Layour and Channel Routing for VLSI Bhatt, Sandeep N. This thesis is motivated by the need for a clearer understanding of various issues in VLSI layout. Within a formal setting, we identify critical properties of circuits that determine the quality of their layouts.

Design and Implementation of a Distributed Program for Collaborative Editing

2023-03-30T03:40:43Z

Design and Implementation of a Distributed Program for Collaborative Editing Seliger, R. This thesis presents the design and implementation of a distributed program for the support of multi-author collaboration on shared documents. The Collaborative Editing System, CES, provides an environment in which authors working on a document can cooperate and coordinate their individual contributions to a single document.

On Playing Well in a Sum of Games

2023-03-30T03:06:51Z

On Playing Well in a Sum of Games Yedwab, Laura Many games are naturally described as a sum of games, e.g., nim and the endgame of Go. Let G ,...,G represent n games. Then a move in the sum G + ...+G consists of picking a component game G and making a move in G .. This thesis analyzes play in a sum of games from three different perspective: computational complexity, approximate solutions, and optimal research algorithms.

A Relative-motion Microworld

2023-03-30T04:20:08Z

A Relative-motion Microworld Morecroft, Linda E. A relative-motion microworld has been designed to aid high-school students in understanding the concepts of relative motion and frames of reference. Relative motion and frames of reference are usually introduced in a high-school physics or mathematics course. Most students, and many teachers too, have difficulty understanding the concepts and applying them to solve problems. The traditional approach to relative motion uses vector algebra. However, vector terminology is complex and it does not allow a mental picture of what is happening to be easily built. students do not understand what it means to be in a different frame of reference and how moving objects appear within this reference frame. Most people have a much more intuitive approach to motion problems.

Equational Theories and Database Constraints

2023-03-30T03:32:34Z

Equational Theories and Database Constraints Cosmadakis, Stavros Stylianos The implication problem for database constraints is central in the fields of automated schema design and query optimization and has been traditionally approached with resolution-based techniques. We present a novel approach to database constraints, using equations instead of Horn clauses.

A Generalized Approach to Equational Unification

2023-03-30T03:36:50Z

A Generalized Approach to Equational Unification Yelick, Katherine Anne Given a set of equational axioms and two terms containing function symbols and variables, the equational unification problem is to find a uniform replacement of terms for the variables that makes the terms provably equal from the axioms. In the variable-only case, the two terms contain only variables and function symbols from the axioms. In the general case, the terms may contain symbols not appearing in the axioms, there may be more than on instance of a set of anxioms, and there may be more than one set of axioms.

A Program for Generating and Analyzing Term Rewriting Systems

2023-03-30T04:02:48Z

A Program for Generating and Analyzing Term Rewriting Systems Forgaard, Randy This thesis presents new results in the use of term rewriting systems for automatic theorem proving. The design and implementation of REVE 2, a computer program that incorporates these results, is described. In addition, an introduction to the basic theory, procedures, and algorithms of term rewriting is provided, in a manner suitable for non-specialists.

Foundations of a Theory of Specification for Distributed Systems

2023-03-30T03:44:16Z

Foundations of a Theory of Specification for Distributed Systems Stark, Eugene W. This thesis investigates a particular approach, called state-transition specification, to the problem of describing the behavior of modules in a distributed or concurrent computer system. A state-transition specification consists of: (1) a state machine, which incorporates the safety or invariance properties of the module, and (2) validity conditions on the computations of the machine, which capture the desired liveness or eventuality properties.

Routing Networks for Packet Communication Systems

2023-03-30T03:59:58Z

Routing Networks for Packet Communication Systems Boughton, George Andrew This thesis examines the design of geographically centralized high performance packet switched networks called routing networks. Each of these networks is intended to be used to interconnect the modules of a highly parallel computer system. The design of such networks is considered in present (1984) technology where only a small number of network nodes can be placed on a single chip and in VLSI technology where a large number of nodes can be placed on a chip.

Reasoning about Preference Models

2023-03-30T04:25:24Z

Reasoning about Preference Models Wellman, Michael Paul Programs that make decisions need mechanisms for representing and reasoning about the desirability of the possible consequences of their choices. This work is an exploration of preference models based on utility theory. The framework presented is distinguished by a qualitative view of preferences and a knowledge-based approach to the application of utility theory. The design for a comprehensive preference modeler is implemented in part by the Utility Reasoning Package (URP), a collection of facilities for constructing and analyzing preference models.

Generic Software for Emulating Multiporocessor Architectures

2023-03-30T04:04:31Z

Generic Software for Emulating Multiporocessor Architectures Soley, Richard Mark The expense of designing, prototyping, and testing a new computer architecture (particularly non-traditional supercomputer architectures, such as the dataflow machine) is enormous. The relative inflexibility of hardware to experimental changes increases the need to fully test a new architectural idea.

Towards a Problem Solving System for Molecular Genetics

2023-03-30T03:31:14Z

Towards a Problem Solving System for Molecular Genetics Koton, Phyllis A. This paper describes a program called GENEX that reasons about the behavior of bacterial operons. It is the first step towards a generalized system that will reason about genetic control mechanisms. The system is easily extensible and able to produce detailed explanations without relying on canned text. Problems in molecular genetics are complicated by uncertainty introduced when reasoning about conformations.

Some Implications of Complexity Theory on Pseudo-random Bit Generation

2023-03-30T03:21:39Z

Some Implications of Complexity Theory on Pseudo-random Bit Generation Trilling, Stephen A recent area of interest in theoretical computer science has been in the construction of so-called pseudo-random bit generators. These generators "stretch" a short sequence of truly random bits into a longer sequence of "pseudo-random" bits. These bits are sufficiently indistinguishable from truly random bits to be useful in deterministic simulation of probabilistic computation.

Synchornizing Clocks in a Distributed System

2023-03-30T04:10:48Z

Synchornizing Clocks in a Distributed System Lundelius, Jennifer Keeping the local times of processes in distributed system synchronized in the presence of arbitrary faults is important in many applications and is an interesting theoretical problem in its own right. In order to be practical, any algorithm to synchronize clocks must be able to deal with process failures and repairs, clock drift, and varying message delivery times, but these conditions complicate the design and analysis of algorithms.

An Approach to Functional Office Automation

2023-03-30T03:52:31Z

An Approach to Functional Office Automation Zarmer, Craig L. Current efforts in office automation emphasize developing tools for supporting common, low-level tasks such as word processing and electronic mail. While they have a wide market, they are not very sophisticated. At the other end of the spectrum are office-specific systems, designed with complete knowledge of the office's operations. Unfortunately, such systems have a market size of one, and so are not very practical.

Parallel Simulation of Digital LSI Circuits

2023-03-30T03:02:40Z

Parallel Simulation of Digital LSI Circuits Aronld, Jeffrey M. Integrated circuit technology has been advancing at a phenomenal rate over the last several years, and promises to continue to do so. If circuit design is to keep pace with fabrication technology, radically new approaches to computer-aided design will be necessary. One appealing approach is general purpose parallel processing. This explores the issues involved in developing a framework for circuit simulation which exploits the locality exhibited by circuit operation to achieve a high degree of parallelism.

Resource Management for the Tagged Token Dataflow Architecture

2023-03-30T03:04:06Z

Resource Management for the Tagged Token Dataflow Architecture Culler, David E. The Tagged Token Dataflow Architecture is a multiprocessor based on the U-interpreter model of dataflow computation. It captures the essential execution mechanism of the U-interpreter precisely; operations are enabled for execution by the availability of operated data. However, computational resources in the model and the machine are viewed quite differently. This thesis addresses four major resource management issues essential to bridge the gap between the U-interpreter and the Tagged Token Dataflow Architecture.

Distributed Name Management

2023-03-30T03:37:34Z

Distributed Name Management Sollins, Karen Rosin The problem being addressed in this research is the design of a naming facility achieving the following goals. First, two functions on names must be supported: accessing a named object, and acting as a place holder for the named object. Second, it must be possible to share those names. Third , communication of the names as well as communication by use of the names must be possible. Finally, feasibility of implementation is a goal.

Qualitative Mathematical Reasoning

2023-03-30T03:08:19Z

Qualitative Mathematical Reasoning Sacks, Elisha Qualitative analysis is the study of abstract causal reasoning. It explores the mechanisms whereby humans analyze complex systems abstractly, while ignoring unimportant and unknown low-level details. Previous research has focused on qualitative simulation techniques, analogous to numerical simulation, that use local information about a system to predict its short-term behavior. This thesis presents a new, calculus based, type of qualitative analysis, called qualitative mathematical reasoning. It derives functional descriptions of systems and uses them to predict global behavior.

Debugging Distributed Computations in a Nest Atomic Action System

2023-03-30T03:56:02Z

Debugging Distributed Computations in a Nest Atomic Action System Chiu, Sheng Yang Concurrent and distributed programs are hard to debug. In this thesis, we argue that structuring activities as nested atomic actions can make debugging such programs much like debugging traditional sequential programs. To support the argument, we present a method for debugging computations in the Argus language and system. Our method is applicable to other action systems since it depends only on the atomicity properties of actions.

Orphan Detection in the Argus System

2023-03-30T04:02:29Z

Orphan Detection in the Argus System Walker, Edward Franklin In a distributed system, an activity running at one node can request another node to perform some service. This request results in an activity being created at the latter node to perform the requested service. The former node may then crash, destroying the activity that requested the service, but leaving behind the activity performing the service. Such surviving are known as orphans [Nelson81]. Orphans are undesirable since they waste resources and can view inconsistent data.

Using Untypes Lambda Calculus to Computer with Atoms

2023-03-30T03:36:35Z

Using Untypes Lambda Calculus to Computer with Atoms Weiss, Paul G. Axioms and verification rules are given for typeless A -calculus with a conditional test for equality between atoms. A semantic completeness theorem is proved and a deterministic evaluator is proposed.

Partial Evaluation as a Means of Language Extensibility

2023-03-30T03:17:33Z

Partial Evaluation as a Means of Language Extensibility Schooler, Richard An optimization technique known as partial evaluation is explored. A partial evaluator optimizes code by making use of static information about program values. Our partial evaluator is designed to optimize mainly applicative code. Un-checked assertions are used to identify applicative constructs in the input code and guide the partial evaluator. Side-effects in the input code are retained but are not optimized.

Efficient Implementation of Applicative Languages

2023-03-30T03:37:35Z

Efficient Implementation of Applicative Languages Ackerman, William B. The analysis of parallelism in an applicative program is much easier than in a program written in a conventional statement-oriented style. This makes it possible for an optimizing compiler to prepare such a program for extremely efficient execution on a suitable enormously parallel computer. This thesis explores the transformations that must be made to achieve very high performance for numerical programs when executed on a computer that uses data flow principles in its operation.

Routing the Power and Ground Wires on a VLSI Chip

2023-03-30T03:02:10Z

Routing the Power and Ground Wires on a VLSI Chip Moulton, Andrew Strout This thesis presents four new algorithms to route noncrossing power and ground trees in one metal layer of a VLSI chip. The implementation of the best algorithm forms MIT's Placement-Interconnect (PI) Project's power-ground routing phase. The input to this power-ground algorithm is a set of rectangular modules on a rectangular chip.

Type Checking in Vimval

2023-03-30T04:01:33Z

Type Checking in Vimval Kuszmaul, Bradley C. A type system is developed for the revised version of the Val programming language (VimVal) which has the following features: (1) Type Inference: allows programs to be written with incomplete type specifications. The type checker infers the types of expressions from their context. (2) Polymorphism: allows modules to be written which operate on more than one type, performing analogous operations on different types of data. (3) higher order functions: are first class data in VIMVAL. (4) Recursive types: a type may to itself.

Coordinating Pebble Motion on Graphs, The Diameter of Permutation Groups, and Applications

2023-03-30T04:23:41Z

Coordinating Pebble Motion on Graphs, The Diameter of Permutation Groups, and Applications Kornhauser, Daniel Martin The problem of memory management in totally distributed computing systems leads to the following movers' problem on graphics: Let G be a graph with n vertices with k < n pebbles number 1...,k on distinct vertices. A move consists of transferring a pebble to an adjacent unoccupied vertex. The problem is to decide whether one arrangement of the pebbles is reachable from another, and to find the shortest sequence of moves to find the rearrangement when it is possible.

Replication Methods for Abstract Data Types

2023-03-30T04:20:23Z

Replication Methods for Abstract Data Types Herlihy, Maurice Peter Replication can enhance the availability of data in a distributed system. This thesis introduces a new method for managing replicated data. We propose new techniques to address four problems associated with replication: (i) the representation and manipulation of replicated data, (iii) on- the-fly reconfiguration, and (iv) enhancing availability in the presence of partitions.

A Constraint Representation and Explanation Facility for Renal Physiology

2024-02-06T14:41:18Z

A Constraint Representation and Explanation Facility for Renal Physiology Asbell, Irwin Current research in Artificial Intelligence has yielded computer programs which have potential to augment the physician's ability to diagnose illness. The medical diagnoses programs of the first generation contain medical facts representing associations between diseases and findings. A most important step is the development of computer programs that have models of physiological processes and have the ability to derive physiological justifications of observed signs and symptoms.

An Abstract Architecture for Parallel Graph Reduction

2023-03-30T03:32:12Z

An Abstract Architecture for Parallel Graph Reduction Traub, Kenneth R. An implementation technique for functional languages that has received recent attention is graph reduction, which offers opportunity for the exploitation of parallelism by multiple processors. While several proposals for parallel graph reduction machines have been made, differing terminology and approaches make these proposals difficult to compare.

Extending Binary Byzantine Agreement to Multivalued Byzantine Agreement

2023-03-30T04:25:25Z

Extending Binary Byzantine Agreement to Multivalued Byzantine Agreement Turpin, Russell; Coan, Brian A. A binary Byzantine agreement algorithm can be extended to produce a multivalued Byzantine agreement algorithm. The resulting multivalued algorithm is cheaper than previously published algorithms when the cost of transmitting values from the multival

Specification and Implementation of Atomic Data Types

2023-03-30T03:53:37Z

Specification and Implementation of Atomic Data Types Weihl, William Edward Maintaining the consistency of long-lived, on-line data is a difficult task, particularly in a distributed system. This dissertation focuses on atomicity as a fundamental organizational concept for such systems. It explores an approach in which

The Design and Implementation of an Online Directory Assistance System

2023-03-30T04:12:48Z

The Design and Implementation of an Online Directory Assistance System Koile, Kimberle This thesis describes the design and implementation of an online directory assistance system called DIRSYS that was modeled after the white pages of a paper telephone book and a full-screen display editor such as Emacs. As the user begins typing a n

Cohesion in Computer Text Generation: Lexical Substitution

2023-03-30T04:00:30Z

Cohesion in Computer Text Generation: Lexical Substitution Granville, Robert Alan This report describes Paul, a computer text generation system designed to create cohesive text. The device used to a achieve this cohesion is lexical substitution. Through the use of syntactic and semantic information, the system is able to determine which type of lexical substitution will provide the necessary information to generate an understandable reference, while no providing so much information that the reference is confusing or unnatural.

A Formal Model of Non-Determinate Dataflow Computation

2023-03-30T03:06:58Z

A Formal Model of Non-Determinate Dataflow Computation Brock, Jarvis Dean Almost ten years ago, Gilles Kahn used the fixed point theory of Dana Scott to define a formal and elegant model of computation for determinate dataflow graphs, networks of determinate processes communicating asynchronously through unbounded channels.

Reliable Object Storage to Support Atomic Actions

2023-03-30T04:24:24Z

Reliable Object Storage to Support Atomic Actions Oki, Brian Masao To preserve the consistency of on-line, long-lived, distributed data in the presence of concurrency and in the event of hardware failures, it is necessary to ensure atomicity and data resiliency in applications. The programming language Argus is designed to support such applications. This thesis investigates the mechanism needed to support the notion of data resiliency present in Argus.

Preliminary Report on the Larch Shared Language*

2023-03-30T03:38:34Z

Preliminary Report on the Larch Shared Language* Guttag, John V.; Horning, J.J. Each member of the Larch family of formal specification languages has a component derived from a programming language and another component common to all programming languages. We call the former interface languages, and the latter the Larch Shared Language.

PADL - A Packet Architecture Description Language: A Preliminary Reference Manual

2023-03-30T04:05:43Z

PADL - A Packet Architecture Description Language: A Preliminary Reference Manual Leung, Clement Kin Cho; William Y-P. PADL is a hardware description language for specifying the behavior and structure of packet communication systems. In such systems, hardware units called modules communicate by sending and receiving packets. The behavior of such a system can be specified by providing the algorithm it executes and the data structures it manipulates. On the other hand, the structure of a system is specified by giving the components or of the system and their interconnection.

A Framework for Solving VSLI Graph Layout Problems

2023-03-30T03:52:22Z

A Framework for Solving VSLI Graph Layout Problems Bhatt, Sandeep N.; Leighton, Frank Thomson This paper introduces a new divide-and-conquer framework for VLSI graph layout. Universally close upper and lower bounds are obtained for important cost functions such as layout area and propagation delay. The framework is also effectively used to design regular and configuration layouts, to assemble large networks of processors using restructurable chips, and to configure networks around faulty processors. it is also shown how good graph partitioning heuristics may be used to develop a provably good layout strategy.

Simulation Tools for Digital LSI Design

2023-03-30T03:26:50Z

Simulation Tools for Digital LSI Design Terman, Christopher J. This thesis proposes a timing simulator (RSIM) based on a uniquely simple transistor model. RSIM allows a designer to determine both the functional and approximate timing characteristics of a MOS network with more accuracy than gate-level simulation, and using larger circuits than are accommodated by circuit analysis programs. In RSIM, transistors are modeled as resistors; the logic states of a transistor's terminal nodes determine its effective resistance.

Dynamic Module Replacement in a Distributed Programming System

2023-03-30T03:14:12Z

Dynamic Module Replacement in a Distributed Programming System Bloom, Toby The replacement of parts of software systems is an important aspect of programming methodology. Most of the research in this area has centered around support for modular construction and the clear separation of interface from implementation. The emphasis has been on producing easily modified static program structures.

A Multiprocessor Emulation Facility

2023-03-30T03:05:29Z

A Multiprocessor Emulation Facility Arvind,; Dertouzos, Michael L.; Lannucci, Robert A. Interest in multiprocessor computer architectures has increased dramatically in the last ten years. However, it has become clear that, in order to effectively use multiprocessors in a general way, some fundamental changes in the model of computation are necessary. Moreover, experimentation in the field is hindered by low-performance simulation tools and high-cost hardware modeling schemes.

Creating a Computer-based Learning Environment for Physically Handicapped Children

2023-03-30T03:14:22Z

Creating a Computer-based Learning Environment for Physically Handicapped Children Valente, Jose Armando The objective of this research is to develop a computer-based learning environment for children physically handicapped by cerebral palsy and to study several issues related to the use of this environment for diagnostic, educational, and remedial purposes. The study is motivated by the desire to better understand the intellectual and motoric deficiencies of cerebral palsied children and to use this information in the development of teaching methods to accommodate each child's particular needs.

An Argument for Soft Layering of Protocols

2023-03-30T03:14:20Z

An Argument for Soft Layering of Protocols Cooper, Geoffrey Howard This thesis is about the efficiency of protocol layering. It examines the technique of protocol layering in an abstract way and finds two major sources of inefficiency in protocol implementations which are caused by the imposition on them of a layered structure. The conventional approach to making layered protocol implementations run efficiently--- for avoiding the sources of inefficiency discussed herein --- are all independent of the protocol specification, and thus all decrease the value of the protocol specification as a guide for implementing protocols.

A Two-tiered Approach to Specifying Programs

2023-03-30T03:49:27Z

A Two-tiered Approach to Specifying Programs Marie Wing, Jeannette Current research in specifications is beginning to emphasize the practical use of formal specifications in program design. This thesis presents a specification approach, a specification language that supports that approach, and some ways to evaluate specifications written that language.

Video Games and Computer Aided Instruction

2023-03-30T04:17:01Z

Video Games and Computer Aided Instruction Krugler, Ken This document will briefly outline the evolution of video games, discuss current video game theory, and describe a program to teach typing on the IBM Personal Computer.

Fundamental Design Problems of Distributed Systems for the Hard-real-time Environment

2023-03-30T04:14:30Z

Fundamental Design Problems of Distributed Systems for the Hard-real-time Environment Mok, Aloysisu Ka-Lau Software designed to function in a hard-real-time environment where strict timing constraints must be met often entails implicit assumptions about a programming language and the underlying system which supports it. Programs which are logically correct, i.e., implement the intended algorithms, may not function correctly if their assumed timing characteristics are not met.

The MDL Programming Environment

2023-03-30T03:02:31Z

The MDL Programming Environment Lebling, P. David

The MDL Programming Language

2023-03-30T03:38:25Z

The MDL Programming Language Galley, S.W.; Pfister, Greg

The MDL Programming Language Primer

2023-03-30T03:56:26Z

The MDL Programming Language Primer Dornbrook, Michael; Blank, Marc

The Impact of Layer Assignment Methods on Layout Algorithms for Integrated Circuits

2023-03-30T04:00:24Z

The Impact of Layer Assignment Methods on Layout Algorithms for Integrated Circuits Pinter, Ron Yair Programs for integrated circuit layout at the module assembly level are typically decomposed into two phases - placement and routing. In this thesis we investigate a third phase which is often implicitly assumed - layer assignment. This thesis studies how layer assignment methodologies interact with placement and routing.

An Office Analysis and Diagnosis Methodology

2023-03-30T03:01:54Z

An Office Analysis and Diagnosis Methodology Sutherland, Juliet With the advent of computer technology designed for use in the office, office analysis, or the process of understanding office work for the purposes of introducing technology, has become increasingly important. The Office Analysis and Diagnosis Methodology (OADM) is a tool to help the analyst gather the data required to decide how, and whether, to introduce office automation technology into a particular office, OADM is best suited for studying semi-structured offices, rather than pure processing operations or special projects. OADM is used to perform a detailed study of a single office and is not designed for use in determining the general automation needs of a large organization.

Office Analysis: Methodology and Case Studies

2023-03-30T03:05:11Z

Office Analysis: Methodology and Case Studies Sirbu, Marvin A., Jr.; Schoichet, Sandor R.; Kunin, Jay S.; Hammer, Michael M.; Sutherland, Juliet B.; Zarmer, Craig L. The Office Analysis Methodology (OAM) is a structured methodology for understanding the current operations of an office. OAM provides guidance in interviewing techniques and approaches to establishing a positive atmosphere for possible office automation efforts. It is designed to be to learn so that people with experience in office work but little experience in analysis can easily perform a study.

On Computing Galois Groups and Its Application To Solvability by Radicals

2023-03-30T03:06:22Z

On Computing Galois Groups and Its Application To Solvability by Radicals Laudau, Susan Eva This thesis presents a polynomial time algorithm for the basic question of Galois theory, checking the solvability by radicals of a monic irreducible polynomial over the integers. It also presents polynomial time algorithms for factoring polynomials over algebraic number fields, for computing blocks of imprimitivity of roots of a polynomial under the transitive action of the Galois group on the roots of the polynomial, and for computing intersections algebraic number fields.

On Bisecting Random Graphs

2023-03-30T03:57:53Z

On Bisecting Random Graphs Bui, Thang Nguyen A bisection of a graph with an even number of vertices is a partition of the vertex set into two disjoint sets of equal size. Given a bisection, the number of edges having one end in each of the two subsets of the bisection is called the size of the bisection. The bisection size of a graph is the minimum size of all possible bisections of the graph.

Internal Consistency of a Distributed Transaction System with Orphan Detection

2023-03-30T03:06:27Z

Internal Consistency of a Distributed Transaction System with Orphan Detection Goree, John A., Jr. This thesis defines a property called "view-serializability", which formalizes internal consistency for a system of nested atomic transactions. Internal consistency is a stronger condition than the usual notion of data base consistency, because it takes into account the views of transactions which will never commit. In a distributed system, local aborts of remote subactions and crashes of nodes can generate orphans: active actions which are descendants of actions that have aborted or are guaranteed to abort.

Concurrency Control for Resilient Nested Transaction

2023-03-30T03:40:13Z

Concurrency Control for Resilient Nested Transaction Lynch, Nancy A. Concurrency control theory is extended to handle nested transactions with failures. The theory is used to present a rigorous correctness proof of a variant of Moss' locking algorithm for implementing nested transactions. The proof has an interesting structure using many levels of abstraction.

Translating Updates of Relational Database Views

2023-03-30T04:25:19Z

Translating Updates of Relational Database Views Cosmadakis, Stavros Stylianos We study the problem of translating updates of data base views. We disambiguate a view update by requiring that a specified view compliment (i.e. a second view which contains all the data base information omitted from the given view) remains constant during the translation. We study some of the computational problems related to the application of this general methodology in the context of relational databases.

A Comparative Study of Computer-aided Clinical Diagnosis

2023-03-30T03:03:56Z

A Comparative Study of Computer-aided Clinical Diagnosis Sherman, Howard Bruce In recent years many computer systems have been developed to assist in medical decision making. Two of these systems in particular, INTERNIST and the Present Illness Program (PIP), have been proposed as suitable for performing general medical diagnosis. However, there has been no way of comparing the performance of these two programs since the medical data used by the programs differs extensively.

Impossibility of Distributed Consensus with One Faulty Process*atio

2023-03-30T04:11:27Z

Impossibility of Distributed Consensus with One Faulty Process*atio Fischer, Michael J.; Lynch, Nancy A.; Paterson, Michael S. The consensus problem involves an asynchronous system of processes, some of which may be unreliable. The problem is for the reliable processes to agree on a binary value. We show that every protocol for this problem has the possibility of nontermination, even with only one faulty process. By way of contrast, solutions are known for the synchronous case, the "Byzantine Generals" problem.

Multilevel Atomicity: A New Correctness Criterion for Database Concurrency Control

2023-03-30T04:02:51Z

Multilevel Atomicity: A New Correctness Criterion for Database Concurrency Control Lynch, Nancy A. Multilevel atomicity, a new correctness criteria for database concurrency control, is defined. It weakens the usual notion of serializability by permitting controlled interleaving among transactions. It appears to be especially suitable for applications in which the set of transactions has a natural hierarchical structure based on the hierarchical structure of an organization.

An Implementation Scheme for Array Operations in Static Data Flow Computers

2023-03-30T03:19:25Z

An Implementation Scheme for Array Operations in Static Data Flow Computers Guang-Rong, Gao The mapping of array operations in VAL programs on a static data flow machine with array memory is studied. The flow dependency graph is introduced as a model of array operations in VAL programs. The balancing and optimization of the flow dependency graphs is presented. The class of well-be VAL programs which can be modeled by flow dependency graphs is specified.

The Design of a Multiprocessor Development System

2023-03-30T03:42:12Z

The Design of a Multiprocessor Development System Anderson, Thomas Lee A multiprocessor development system has been designed and a prototype system is being constructed. The system, known as Concert, is intended to support multiprocessor research efforts at M.I.T. The motivation for Concert and the project history are summarized briefly. Some intended applications are also identified.

Display Management in an Integrated Office

2023-03-30T03:30:19Z

Display Management in an Integrated Office Rosenstein, Larry S. Advances in technology now make it possible to build office workstations that have a large amount of local computing power and high-resolution output devices. Such workstations can be used for various office applications, such as document preparation, personal databases, and electronic mail.

Efficient Modeling for Short Channel MOS Circuit Cimulation

2023-03-30T03:46:23Z

Efficient Modeling for Short Channel MOS Circuit Cimulation Johnson, Mark Griffin Existing circuit models for short-channel MOS transistors represent a compromise between speed and ease of use. Empirical models are very fast to evaluate, but their parameters must be fitted from experimental measurements. Theoretical models require longer computation time, but they may be used to predict the performance of new, unmeasured MOS technologies since their parameters are not curve-fitted from experimental data.

Automatic Synthesis of Implementations for Abstract Data Types from Algebraic Specifications

2023-03-30T03:47:44Z

Automatic Synthesis of Implementations for Abstract Data Types from Algebraic Specifications Srivas, Mandayam K. Algebraic specifications have been used extensively to prove properties of abstract data types and to establish the correctness of implementations of data types. This thesis explores an automatic method of synthesizing implementations for data types from their algebraic specifications.

Analysis and Specification of Office Procedures

2023-03-30T03:25:23Z

Analysis and Specification of Office Procedures Kunuin, Jay S. Conventional approaches to "office automation" focus on the lowest common denominator of office work: typing, filing, filling in forms, etc. As a consequence, the process of office systems analysis lacks tools and techniques that address the office in terms of business functions rather than as manipulation of paper artifacts.

Layouts for the Shuffle-exchange Graph and Lower Bound Techniques for VLSI

2023-03-30T04:00:39Z

Layouts for the Shuffle-exchange Graph and Lower Bound Techniques for VLSI Leighton, Frank Thomson The thesis is divided into two parts. In the first part, we describe and analyze several new VLSI layouts for the shuffle-exchange graph. These include:1) an asymptotically optimal, (N /log N)-area layout for the N-node shuffle-exchange graph, and 2) several practical layouts for small shuffle-exchange graphs.

Data Communications via Cable Television Networks: Technical and Policy Considerations

2023-03-30T03:54:58Z

Data Communications via Cable Television Networks: Technical and Policy Considerations Estrin, Deborah Lynn Cable television networks offer peak communication data rates that are orders of magnitude greater than the telephone local loop. Although one-way television signal distribution continues to be the primary application of cable television systems, the cable television network can be used for two-way data communication.

Procedural Reflection in Programming Languages Volume I

2023-03-30T03:05:50Z

Procedural Reflection in Programming Languages Volume I Smith, Brian Cantwell We show how a computational system can be constructed to "reason," effectively and consequentially, about its own inferential processes. The analysis proceeds in two parts. First, we consider the general question of computational semantics, rejecting traditional approaches, and arguing that the declarative and procedural aspects of computational symbols (what they stand for, and what behaviour they engender) should be analysed independently, in order that they may be coherently related.

A Computer System for Decision Analysis in Hodgkins Disease

2023-03-30T03:23:44Z

A Computer System for Decision Analysis in Hodgkins Disease Rutherford, Cynthia, J.; Davies, Byron; Barnett, Arnold I.; Desforges, Jane F. This report draws together the diverse strands involved in developing a unique computer-based system to stage and manage Hodgkins Disease (HD). Those of us worked on the final version of this project included two hematologists, a computer scientist, and a statistician.

The Design of a Routing Service for Campus-wide Internet Transport

2023-03-30T03:41:41Z

The Design of a Routing Service for Campus-wide Internet Transport Singh, Vineet A campus-wide network requires many subnetworks connected by gateways and it has a relatively loose administration. Modularization of network implementing is important in this environment to make efficient use of ever-improving technologies and protocols.

The Complexity of Concurrency Control for Distributed Databases

2023-03-30T03:47:57Z

The Complexity of Concurrency Control for Distributed Databases Kanellakis, Paris C. This study is an analysis of the distributed version of data base concurrency control. It provides concrete mathematical evidence that the distributed problem is an inherently more complex task than the centralized one. The notions of transaction, concurrency, history, serializability, scheduler, etc, for centralized databases are now well-understood both from a theoretical and a practical point of view.

Derived Pairs, Overlap Closures, and Rewrite Dominoes: New Tools for Analyzing Term Rewriting Systems

2023-03-30T03:47:00Z

Derived Pairs, Overlap Closures, and Rewrite Dominoes: New Tools for Analyzing Term Rewriting Systems Guttag, John V.; Kapur, Deepak; Musser, David R. Starting from the seminal work of Knuth and Bendix, we develop several notions useful in the study of term rewriting systems. In particular we introduce the notions of "derived pairs" and "overlap closure" and show that they are useful in analyzing sets of rewrite rules for various properties related to termination. We also introduce a new representation, based on rewrite dominoes, for rewrite rules and sequences of rewrites.

Causal Representation of Patient Illness for Electrolyte and Acid-base Diagnosis

2023-03-30T04:03:41Z

Causal Representation of Patient Illness for Electrolyte and Acid-base Diagnosis Patil, Ramesh S. Much of the medical knowledge in the first generation Al in Medicine programs is phenomenological; that is, it describes the associations among phenomena without knowledge of the underlying causal mechanisms. Although these AIM programs provide a good first approximation to the way clinicians reason, they fail to produce clinicians reasoning based on a deaper understanding of the phenomens.

An Ease of Use Evaluation of an Integrated Editor and Formatter

2023-03-30T03:54:45Z

An Ease of Use Evaluation of an Integrated Editor and Formatter Good, Michael Etude is an integrated text editor and formatter that was designed to be easy to learn and easy to use. To measure Etude's success in meeting these goals, twenty-one computer-naive temporary office workers were taught to use Etude in a controlled experiment. Ninety percent of the subjects were able to create and edit letters after a training period of less than two hours and twenty minutes, though they were not able to perform these tasks as quickly as they could when using a typewriter.

A Data Flow Architecture with Improved Asymptotic Performance

2023-03-30T03:23:11Z

A Data Flow Architecture with Improved Asymptotic Performance Thomas, Robert E. Large scale integration presents a unique opportunity to design a computer compromising large numbers of small, inexpensive processors. This paper presents a design for such a machine based on the asynchronous and functional semantics of data flow.

Interactive Debigging in a Distributed Computational Envrionment

2023-03-30T04:15:57Z

Interactive Debigging in a Distributed Computational Envrionment Schiffenbauer, Robert David

Propositional Dynamic Logic of Looping and Converse

2023-03-30T03:06:52Z

Propositional Dynamic Logic of Looping and Converse Streett, Robert S. Dynamic logic [5,6,15,16] applies concepts from modal logic to a relational semantics of programs to yield various systems for reasoning about the before-after behavior of programs. Analogues to the modal logic assertions ?p (possibly p) and ?p(necessarily p) are the dynamic logic constructs p and [a]p. If a is a program and p is an assertion about the state of a computation, then ,p asserts that after executing a, p can be the case, and [a]p asserts that after executing a, p must be the case.

High Level VAL Constructs in a Static Data Flow Machine

2023-03-30T03:42:55Z

High Level VAL Constructs in a Static Data Flow Machine Todd, Kenneth Wayne The Dennis-Misunas Form 1 Data Flow Machine can best be described as a static and scalar machine. Despite these two limiting characteristics, it is still possible to translate the whole of the functional programming language VAL into the base language of this machine. Methods for translating the various high constructs of VAL are presented which exploit the parallelism inherent in programs written in VAL mainly by pipelining through a single expression (vertical parallelism) rather than employing many copies of that same expression (horizontal parallelism), although the latter is not ruled out.

A Switch-level Simulation Model for Integrated Logic Circuits

2023-03-30T03:05:41Z

A Switch-level Simulation Model for Integrated Logic Circuits Bryant, Randal Everitt Switch-level simulators model a metal oxide semiconductor (MOS) large scale integrated (LSI) circuits as a network of transistor "switches". They can simulate many aspects of MOS circuits which cannot be expressed in the Boolean logic gate model, such as bidrecttional pass transistors, dynamic storage, and charge sharing.

A Design Methodology for Self-time Systems

2023-03-30T03:48:26Z

A Design Methodology for Self-time Systems Singh, Narinder Pal This thesis presents a design methodology for self-timed systems which will be extremely attractive for implementing systems in VLSI. Self-timed systems are characterized by the absence of a timing reference to which all operations are synchronized.

Application of Data Flow Architecture to Computer Music Synthesis

2023-03-30T03:39:13Z

Application of Data Flow Architecture to Computer Music Synthesis Cesari, Carol Andrea A computer music synthesis system is the most flexible of synthesis systems. It offers a composer extensive control over the sound of his piece. A user of such a system describes his composition in some synthesis language. The computer uses this description to calculate samples of a voltage waveform that can be fed to D/A converters at a specified sampling rate.

Semiautomatic Translation of Cobol In Hibol

2023-03-30T04:14:25Z

Semiautomatic Translation of Cobol In Hibol Faust, Gregory Gerard A severe software crisis is currently being experienced by the data processing community due to intolerable maintenance costs. A system is introduced to reduce those costs by the translation of existing COBOL software into HIBOL; a very high level language that is significantly easier to maintain.

Protecting Externally Supplied Software in Small Computers

2023-03-30T03:43:41Z

Protecting Externally Supplied Software in Small Computers Kent, Stephen T. The increasing decentralization of computing resources and the proliferation of personal and small business computers create new problems in computer security. One such problem is the protection of externally supplied software, i.e., software supplied by other than the users/owners of these small computers. In the case of personal and small business computers, proprietary software serves as the primary example.

An Integrated Approach to Formatted Document Production

2023-03-30T03:08:46Z

An Integrated Approach to Formatted Document Production Ilson, Richard Recent advances in printing technology have reduced the cost of typeset quality printers. Unfortunately, the production of attractively formatted documents requires typographic skill and special training on computer-based text processing systems. The principal characteristics of Etude are that it embodies substantial typographic expertise, and is based on concepts familiar to untrained users . Furthermore, Etude provides a real-time display facility that allows the results of editing and formatting operations to be seen immediately. Thus, Etude supports the entire process of producing decorously formatted documents.

Recovery of the Swallow Repository

2023-03-30T03:02:37Z

Recovery of the Swallow Repository Arens, Gail C. This thesis presents the design of a set of recovery mechanisms for the Swallow repository. Swallow is a distributed data storage system that supports highly reliable long term storage of arbitrary sized data objects with special mechanisms for implementing multi-site atomic actions. The Swallow repository is a data storage server that keeps permanent data in write-once stable storage such as optical disk.

Producing Explanations and Justifications of Expert Consulting Programs

2023-03-30T03:03:19Z

Producing Explanations and Justifications of Expert Consulting Programs Swartout, William R. Traditional methods for explaining programs provide explanations by converting to English the code of the program or traces of the execution of that code. While such methods can provide adequate explanations of what the program does or did, they typically cannot provide justifications of the code without resorting to canned-text explanations. That is, such systems cannot tell why what the system is doing is a reasonable thing to be doing.

Fault Tolerance in Packet Communication Computer Archiectures

2023-03-30T03:43:10Z

Fault Tolerance in Packet Communication Computer Archiectures Leung, Clement Kin Cho It is attractive to implement a large scale parallel processing system as a self-timed hardware system with decentralized control and to improve maintainability and availability in such a system through fault tolerance. In this thesis we show how to tolerate hardware failures in a self-timed hardware system with a packet communication architecture, designed to execute parallel programs organized by data flow concepts.

Computers and People: Personal Computation

2023-03-30T04:27:02Z

Computers and People: Personal Computation Turkle, Sherry In the January 1975 issue of Popular Electronics, MITs, short for Micro Instrumentation and Telementry System, a small computer company in Albequerque, New Mexico, announced the Altair, a computer small enough to sit on a desktop, powerful enough to support high level language programming, and that you could build for only $429.

Algorithms for Integrated Circuit Layout: An Analytic Approach

2023-03-30T03:17:12Z

Algorithms for Integrated Circuit Layout: An Analytic Approach LaPaugh, Andrea Suzanne In this thesis, the problem of designing the layout of integrated circuits is examined. The layout of an integrated circuit specifies the position of the chip of functional components and wires interconnecting the components. We use a general model

Interprocedural Data Flow Analysis in the Presence of Pointers, Procedure Variables, and Label Variables

2023-03-30T04:17:13Z

Interprocedural Data Flow Analysis in the Presence of Pointers, Procedure Variables, and Label Variables Weihl, William Edward The compilation of highly modular programs requires extensive interprocedural analysis in order to produce reasonable object code. Such analysis is greatly complicated when the source language contains such constructs as procedure variables and label variables.

A Survey of the Logic of Effective Definitions

2023-03-30T04:07:06Z

A Survey of the Logic of Effective Definitions Tiuryn, J. LED, the Logic of Effective Definitions, is an extension of first order predicate calculus used for making assertions about programs. Programs are modeled as effective definitional schemes (following Friedman). Logical properties of LED and its relations to classical logics and other programming logics are surveyed.

On Memory Limitations in Natural Language Processing

2023-03-30T03:16:30Z

On Memory Limitations in Natural Language Processing Church, Kenneth Ward This paper proposes a welcome hypothesis: a computationally simple device is sufficient for processing natural language. Traditionally it has been argued that processing natural language syntax requires very powerful machinery. Many engineers have come to this rather grim conclusion: almost all working parsers are actually Turing Machines (TM). For example, Woods specifically designed his Augmented Transition Networks (ATNs) to be Turing Equivalent.

Data Driven Loops

2023-03-30T03:41:57Z

Data Driven Loops Ruth, Gregory R. The notion of the data driven loop arises in connection with our work in the Very High Level Language HIBOL and the automatic programming system (ProtoSystem I) that supports it. Although the concept is of general interest outside of VHLL's and automatic programming, we find it profitable to use HIBOL as a vehicle for our discussion and a means of narrowing the scope of our discussion. Therefore we first present description of the domain which HIBOL treats.

Management of Object Histories in the Swallow Repository

2023-03-30T03:43:37Z

Management of Object Histories in the Swallow Repository Svobodova, Liba SWALLOW is an experimental distributed data storage system that provides personal computers with a uniform interface to their local data and the data stored in shared remote servers called repositories. The SWALLOW repositories provide reliable, secure reliable, secure, and efficient long-term storage for both very small and very large objects and support updating of a group of objects at one or several repositories in a single atomic action.

Simulations Amond Multidimensional Turing Machines

2023-03-30T03:48:49Z

Simulations Amond Multidimensional Turing Machines Loui, Michael Conrad This thesis presents three independent papers: nearly optimal on-line simulations among multidimensional Turing machines, a space bound for one-tape multidimensional Turing machines, and new proofs in the pebble game.

Representation and Analysis of Real-Time Control Structures

2023-03-30T04:07:25Z

Representation and Analysis of Real-Time Control Structures Archer, Rowland F., Jr. A new notation is introduced for representing real-time scheduling at the task and event level. These schedules are called control structures. The primary constructs included which direct the flow of control are sequencing, iteration, and preemption. Additional notation allows the representation of interrupt masking, task termination by external events, task restart as well as resumption from the point of preemption and codestripping. Algorithms are given for finding the presentation structures of a given control structure in the notation.

Safety and Optimization Transformations for Data Flow Programs

2023-03-30T03:37:24Z

Safety and Optimization Transformations for Data Flow Programs Montz, Lynn Barbara The data flow concept of computation seeks to achieve high performance by allowing concurrent execution of instructions based on the availability of data. This thesis explores the translation of a subset of the high level languages VAL to data flow graphs. The major problem in performing this translation for the target machine. the Dennis-Misunas data flow computer, stems from the restriction that graph execution sequences place at most one value on any given are at any time. The data/acknowledge are pair transformation is introduced as a means of implementing this required operational behavior. Its effect on data flow graph operation is subsequently explored as it relates to correctness and performance.

Artwork Analysis Tool for VLSI Circuits

2023-03-30T03:35:40Z

Artwork Analysis Tool for VLSI Circuits Baker, Clark Marshall Current methods for designing VLSI chips do not insure that the chips will perform correctly when manufactured. Because the turn around time on chip fabrication varies from a few weeks to a few months, a scheme other than "try it and see if it works" is needed. Checking of chips by hand simulation and visual inspection of check plots will not cash all of the errors. In addition, the number of transistors per chip is likely to increase from ten thousand to over a million in the next few years.This increase in complexity precludes any manual verification methods; some better method is needed.

The Complexity of Monotone Boolean Functions and an Algorithm for Finding Shortest Paths on a Graph

2023-03-30T04:18:42Z

The Complexity of Monotone Boolean Functions and an Algorithm for Finding Shortest Paths on a Graph Bloniarz, Peter Anthony The first part of this thesis considers the complexity of Boolean functions. The main complexity measures used are the number of gates in combinational networks and the size of Boolean formulas. The case of monotone realizations, using only the operations AND and OR, of monotone functions is emphasized.

Towards a Theory for Abstract Data Types

2023-03-30T04:09:39Z

Towards a Theory for Abstract Data Types Kapur, Deepak A rigorous framework for studying immutable data types having nondeterministic operations and operations exhibiting exceptional behavior is developed. The framework embodies the view of a data type taken in programming languages, and supports hierarchical and modular structure among data types.

Scheduling Task Systems with Resources

2023-03-30T04:15:35Z

Scheduling Task Systems with Resources Lloyd, Errol Lynn Minimum execution time scheduling of task systems with resources has been the subject of several papers over the past few years. The model used for much of this work assumes that the resources in the system are continuous. That the, there is one unit of each resource, and a task may require any portion of that unit during its execution.

A Concept of Independence with Applications in Various Fields of Mathematics

2023-03-30T04:26:58Z

A Concept of Independence with Applications in Various Fields of Mathematics Levin, Leonid A. We use Kolmogorov's algorithmic approach to information theory to define a concept of independence of sequences, or equivalently, the boundedness of their mutual information. This concept is applied to probability theory, intuitionistic logic, and the theory of algorithms.

Transmitting Abstract Values in Messages

2023-03-30T03:52:26Z

Transmitting Abstract Values in Messages Herlihy, Maurice Peter This thesis develops primitives for a programming language intended for use in a distributed computer system where individual nodes may have different hardware or software configurations. Our primitives are presented as extensions to the CLU language.

Automatic Extension of an Augmented Transition Network Grammar for Morse Code Conversations

2023-03-30T03:15:39Z

Automatic Extension of an Augmented Transition Network Grammar for Morse Code Conversations Kaiser, Gail E. This report describes a 'learning program' that acquires much of the knowledge required by a parsing system that processes conversations in a 'natural' language akin to ham-radio jargon. The learning program derives information from example sentence taken from transcripts of actual conversations, and uses this knowledge to extend the 'core' augmented transition network (ATN) grammar.

The Complexity of the Maximum Network Flow Problem

2023-03-30T03:36:06Z

The Complexity of the Maximum Network Flow Problem Baratz, Alan Edward This thesis deals with the computational complexity of the maximum network flow problem. We first introduce the basic concepts and fundamental theorems upon which the study of "max-flow" has been built. We then trace the development of max-flow algorithms from the original "labeling algorithm" of Ford and Fulkerson, through a recent 0 (V-E-log 2 V) algorithm due to Galil and Naamad.

Automatic Verification of Serializers

2023-03-30T03:37:43Z

Automatic Verification of Serializers Atkinson, Russ R. This thesis is concerned with the problem of controlling concurrent access to shared data. A language construct is proposed to enforce such control; a specification language is defined to describe the formal requirements of such control; and verification techniques are given to prove that instances of the construct satisfy their specifications.

An Abstract Implementation for a Generalized Data Flow Language

2023-03-30T03:07:58Z

An Abstract Implementation for a Generalized Data Flow Language Weng, Kung-Song In this thesis we are concerned with issues arising from the need to achieve concurrency of operation with a computation on a large scale. Several factors contribute toward increasing interest in systems capable of exploiting the concurrency of computation.

Incomprehensible Computer Systems: Knowledge Without Wisdom

2023-03-30T03:33:14Z

Incomprehensible Computer Systems: Knowledge Without Wisdom Rosenberg, Ronni Lynne An analysis of the incomprehensibility of large, complex computer systems is made. The thesis is that there is a strong relationship between system incomprehensibility and the necessity to trust computer systems. A cogent definition of incomprehensibility in computer system is established, with common themes drawn from interdisciplinary literature dealing with computers and society.

CLU Reference Manual

2023-03-30T03:12:47Z

CLU Reference Manual Liskov, Barbara; Atkinson, Russ R.; Bloom, Toby; Moss, J. Eliot B.; Schaffert, Craig; Scheifler, Bob; Snyder, Alan This document serves both as an introduction to CLU and as a language reference manual. Sections 1 through 4 present an overview of the language. These sections highlight the essential features of CLU, and discuss how CLU differs from other, more conventional, languages.

Toward a Computational Theory of Indirect Speech Acts

2023-03-30T04:12:00Z

Toward a Computational Theory of Indirect Speech Acts Brown, Gretchen P. The variety of surface forms that may be used to convey a given speech act pose a major problem in modeling task-oriented (and other) dialogues. Many such forms are so-called indirect speech acts, that is, surface form does not correspond to the (or one) intended speech act.

Abstract Model Specifications for Data Abstractions

2023-03-30T03:35:37Z

Abstract Model Specifications for Data Abstractions B_rzin_, Valdis Andris A data abstraction introduces a data type with a hidden representation. Specifications of data abstractions are required to allow the data to be described and used without reference to the underlying representation. There are two main approaches to specifying data abstractions, the abstract model approach and the axiomatic approach.

Denotational Semantics of Determinate and Non-Determinate Data Flow Programs

2023-03-30T04:03:24Z

Denotational Semantics of Determinate and Non-Determinate Data Flow Programs Kosinski, Paul Roman Among its other characteristics, a programming language should be conducive to writing modular program's, be able to express parallelism and non-determinate behavior, and it should have a cleanly formalizable semantics. Data flow programming languages have all these characteristics and are especially amenable to mathematization of their semantics in the denotational style of Scott and Strachey.

Copying Complex Structures in a Distributed System

2023-03-30T03:54:08Z

Copying Complex Structures in a Distributed System Sollins, Karen Rosin This thesis presents a model of a distributed system. The universe of objects in the distributed system is divided into mutually exclusive sets, each set corresponding to a context. This model allows naming beyond the context boundaries, but limits communication across such boundaries to message passing only.

VAL- A Value-oriented Algorithmic Language: Preliminary Reference Manual

2023-03-30T03:41:06Z

VAL- A Value-oriented Algorithmic Language: Preliminary Reference Manual Ackerman, William B.; Dennis, Jack B. The programming language VAL (Value-Oriented Algorithmic Language) is designed for expressing algorithms for execution on computers capable of highly concurrent operation. More specifically, the application area to be supported is numerical computation which strains the limits of high performance machines, and primary targets for translation of VAL programs are data driven machines of the form under development by the Computation Structures Group of the MIT Laboratory for Computer Science for high performance numerical computation.

Storage and Access Costs for Implementations of Variable - Length lists

2023-03-30T03:07:51Z

Storage and Access Costs for Implementations of Variable - Length lists Brown, Donna Jean Consider a machine with a cellular memory used to store a list X , where X is a finite alphabet and i N. We investigate the machine representation of such a list and the implementation of common list operations such as determining the i th element and adding or deleting an element.

Analysis of the Simple Code for Dataflow Computation

2023-03-30T03:48:09Z

Analysis of the Simple Code for Dataflow Computation Myers, John M. We analyze a problem in hydrodynamics from the standpoint of computation on a data flow compute that is not yet fully specified, with the objectives of helping to further specify the computer and helping to develop VAL as its source language. Lawrence Liver,ore Laboratory supplied the algorithm for hydrodynamics, including heat flow, as a 1749-line FORTRAN code called SIMPLE.

Distributed Computer Systems: Structure and Semantics

2026-02-05T21:15:42Z

Distributed Computer Systems: Structure and Semantics Svobodova, Liba; Liskov, Barbara; Clark, David D This report describes an ongoing project in the area of design of distributed systems. The goal is to develop an effective programming system that will support well-structured design implementation, maintenance and control of distributed processing applications.

Probabilistic Algorithm in Finite Fields

2023-03-30T04:22:32Z

Probabilistic Algorithm in Finite Fields Rabin, Michael O. We present probabilistic algorithms for the problems of finding an irreducible polynomial of degree n over a finite field, finding roots of a polynomial and factoring the polynomial into its irreducible factors over a finite field. All of these problems are of importance in algebraic coding theory, algebraic symbol manipulation, and number theory.

Digitalized Signatures and Public-key Functions as Intractable as Factorization

2023-03-30T04:19:21Z

Digitalized Signatures and Public-key Functions as Intractable as Factorization Rabin, Michael O. We introduce a new class of public-key functions involving a number n = p.q having two large prime factors. As usual, the key n is public, while p and q are the private key used by the issuer for production of signatures and function inversion. These functions can be used for all the applications involving public-key functions proposed by Diffie and Hellman [ 2 ], including digitalized signatures.

Synchronization Mechanism for Modular Programming Language

2023-03-30T03:59:08Z

Synchronization Mechanism for Modular Programming Language Bloom, Toby Any programming language that supports concurrency needs a synchronization construct with which to express access control for shared resources. This thesis examines synchronization constructs from the standpoint of language design for reliable software. The criteria a synchronization mechanism must satisfy to support construction of reliable, easily maintainable concurrent software are defined.

Serializability of Concurrent Data Base Updates

2023-03-30T03:03:00Z

Serializability of Concurrent Data Base Updates Papadimitriou, Christos H. A sequence of interleaved user transactions in a data base system may not be serializable, i.e., equivalent to some sequential execution of the individual transactions. Using a simple transaction model we show that recognizing the transaction histories which are serializable is an NP-complete problem.

A Machine Architecture to Support an Object-Oriented Language

2023-03-30T03:07:17Z

A Machine Architecture to Support an Object-Oriented Language Snyder, Alan In object-oriented languages (e.g., LISP, Simula, and CLU), all (or most) data objects used by a program are implicitly allocated from a free-storage area and are accessed via fixed-size references. The storage for an object is automatically reclaimed (garbage collected) when the object is no longer accessible to the program.

A Microcomputer Network Simulation System

2023-03-30T03:13:52Z

A Microcomputer Network Simulation System Krizan, Brock Collins The design, development and use of cost-effective computer networks require information about system behavior given a variety of network structures and operational policies. Because computer networks are complex systems whose behavior is generally not intuitively understood, there is a need for system analysis tools to provide a wide range of performance information.

Robust Concurrency Control for a Distriuted Information System

2023-03-30T03:52:52Z

Robust Concurrency Control for a Distriuted Information System Montgomery, Warren A.

Naming and Synchornization in a Decentralized Computer System

2023-03-30T03:51:25Z

Naming and Synchornization in a Decentralized Computer System Reed, David Patrick In this dissertation a new approach to the synchronization of accesses to shared data objects is developed. Traditional approaches to the synchronization problems of shared data accessed by concurrently running computations have relied on mutual exclusion--the ability of one computation to stop the execution of other computations that might access or change shared data accessed by that computation.

Real-time Control Structures for Block Diagram Schemata

2023-03-30T04:13:26Z

Real-time Control Structures for Block Diagram Schemata Teixeira, Thomas Joseph Block diagram schemata model computation systems in the context of an external environment. The environment imposes various constraints on the real-time performance of any implementation of a block diagram schema. The model is used to provide precise definitions of real-time performance. The portion of the implementation that affects the real-time performance is called the control structure.

Synthesis of Synchronization Code for Data Abstractions

2023-03-30T04:16:26Z

Synthesis of Synchronization Code for Data Abstractions Laventhal, Mark Steven Synchronization code is necessary to control shared access of an abstract data object in a parallel-processing environment. This thesis explores an approach in which a synchronization property can be specified in a high-level nonprocedural language, and an implementation for the specified property can be synthesized algorithmically.

A Formalization of the State Machine Specification Technique

2023-03-30T03:04:16Z

A Formalization of the State Machine Specification Technique Principato, Robert N., Jr. This thesis develops the state machine specification technique, a formal specification technique for data abstractions based on Parnas' work on specifying software modules.

A Denotational Semantics of CLU

2023-03-30T03:50:57Z

A Denotational Semantics of CLU Scheifler, Robert W. A denotational semantics of CLU, an object-oriented language supporting data abstractions, is presented. The definition is based on Scott's lattice-theoretic approach to the theory of computation. Modules, the basic unit of compilation, are represented in terms of a set of recursively defined domains called the abstract syntax.

Logics of Programs: Axiomatics and Descriptive Power

2023-03-30T04:25:13Z

Logics of Programs: Axiomatics and Descriptive Power Harel, David This thesis is concerned with the development of mathematical tools for reasoning about computer programs. The approach is to design and investigate the properties of various dynamic logics with an emphasis on useful expressive power and adequate proof theory.

The Specification of Code Generation Algorithms

2023-03-30T03:47:32Z

The Specification of Code Generation Algorithms Terman, Christopher J. This thesis addresses the problem of automatically constructing the code generation phrase of a compiler from a specification of the source language and target machine. A framework for such a specification is presented in which information about language and machine dependent semantics in incorporated as a set of transformation on an internal representation of the source language program.

Actor Systems for Real-time Computation

2023-03-30T04:07:51Z

Actor Systems for Real-time Computation Baker, Henry Givens, Jr. Actor theory was invented by Hewitt and collaborators as a synthesis of many of the ideas from the high-level languages LISP, GEDANKEN, SMALLTALK, SIMULA-67, and others. Actor theory consists of a group of active objects called Actors, which communicate by passing messages to one another.

Final Report of the Multics Kernal Design Project

2026-02-05T21:17:47Z

Final Report of the Multics Kernal Design Project Schroeder, Michael D.; Clark, David D; Saltzer, Jerome H.; Wells, D.H. We describe a plan to create an auditable version of Multics. The engineering experiments of that plan are now complete. Type extension as a design discipline has been demonstrated feasible, even for the internal workings of an operating system, where many subtle intermodule dependencies were discovered and controlled.

On Time-space Classes and Their Relation to the Theory of Real Addition

2023-03-30T03:45:07Z

On Time-space Classes and Their Relation to the Theory of Real Addition Bruss, Anna R. A new lower bound on the computational complexity of the theory of real addition and several related theories is established: any decision procedure for these theories requires either space n2 or nondeterministic time 2en2 for some constant E> 0 and infinitely many n.

Actors and Continuous Functionals

2023-03-30T04:15:52Z

Actors and Continuous Functionals Hewitt, Carl; Baker, Henry Givens, Jr. This paper presents precise versions of some "laws" that must be satisfied by computations involving communicating parallel processes. The laws take the form of stating plausible restrictions on the histories of computations that are physically realizable .

Attribute Partitioning in a Self-adaptive Relational Data Base Systems

2023-03-30T03:13:00Z

Attribute Partitioning in a Self-adaptive Relational Data Base Systems Niamir, Bahram One technique that is sometimes employed to enhance the performance of a data base management system is known as attribute partitioning. This is the process of dividing the attributes of a file into subfiles that are stored separately. By storing together those attributes that are frequently requested together by transactions, and by separating those that are not, attribute partitioning can reduce the number of pages that must be transferred from secondary storage to primary memory in order to process a transaction.

Specifications and Verification Techniques for Parallel Programs Based on Message Passing Semantics

2023-03-30T03:30:05Z

Specifications and Verification Techniques for Parallel Programs Based on Message Passing Semantics Yonezawa, Akinori This thesis presents formal specification and verification techniques for both serial and parallel programs written in SIMULA-like object oriented languages. These techniques are based on the notion of states of individual objects which are defined uniformly in serial and parallel computations. They can specify and verify the behavior of data and procedural objects in multi-process environments, thus overcoming some of the difficulties in dealing with parallelism which characterized previous work on formal specifications for abstract data types.

Abstract Data Types in Stack Based Languages

2023-03-30T04:18:57Z

Abstract Data Types in Stack Based Languages Moss, J. Eliot B. Abstract data types are the basis of an emerging methodology of computer programming. The only existing languages supporting abstract data types directly, CLU and Simula, both require compacting garbage collection, and thus they are not suitable for many applications. This thesis presents the design of a new language incorporating abstract data types; the language requires only a run-time stack, and not garbage collection.

Formal Specifications for Packet Communication Systems

2023-03-30T04:05:20Z

Formal Specifications for Packet Communication Systems Ellis, David J. One of the most difficult tasks facing computer scientists is that of designing systems and making sure that they perform their intended functions correctly. As computer systems have grown in size and complexity, the problems of system design and verification have become increasingly acute.

Simulation of Packet Communication Architecture Computer Systems

2023-03-30T03:56:08Z

Simulation of Packet Communication Architecture Computer Systems Bryant, Randal R. Simulations of computer systems have traditionally been performed on a single sequential computer, even if the system to be simulated contains a number of components which operate concurrently.

A Structure Memory for Data Flow Computers

2023-03-30T03:13:11Z

A Structure Memory for Data Flow Computers Ackerman, William B. A data flow computer is one which achieves enormous concurrency of instruction execution through a machine architecture that acts directly on a data dependency graph of the program.

Deadlock Detection in Computer Networks

2023-03-30T03:53:20Z

Deadlock Detection in Computer Networks Goldman, Barry The problem of detecting process deadlocks is common to transaction oriented computer systems which allow data sharing. Several good algorithms exist for detecting process deadlocks in a single location facility. However, the deadlock detection problem becomes more complex in a geographically distributed computer network due to the fact that all the information needed to detect a deadlock is not necessarily available in a single node, and communications delays may lead to synchronization problems in getting an accurate view of the network state.

Facilitating Interprocess Communication in a Heterogeneous Network Environment

2023-03-30T04:22:00Z

Facilitating Interprocess Communication in a Heterogeneous Network Environment Levine, Paul H. Passing information among processors with different internal data formatting schemes has proven to be a major complication to computer networking efforts. Data format translation is necessary to support information exchange in a heterogeneous network environment. Three strategies for performing this translation for communications between a message sender translation by an intermediate translator, and the use of a standard intermediate format.

A Framework for Processing Dialogue

2023-03-30T03:01:47Z

A Framework for Processing Dialogue Brown, Gretchen P. This report describes a framework for handling mixed-initiative English dialogue in a console session environment, with emphasis on recognition. Within this framework, both linguistic and non-linguistic activities are modelled by structures called methods, which are a declarative form of procedural knowledge. Our design focus on units of linguistic activity larger than the speech act, so that the pragmatic and semantic context of an utterance can be used to guide its interpretation. also important is the treatment of indirect speech acts,e.g., the different ways to ask a question, give a command, etc.

The Complexity of the Finite Containment Problem for Petri Nets

2023-03-30T04:12:36Z

The Complexity of the Finite Containment Problem for Petri Nets Mayr, Ernst Wilhelm If the reachability set of a Petri net (or, equivalently, vector addition system) is finite it can be effectively constructed. Furthermore, the finiteness is decidable. Thus, the containment and equality problem for finite reachability sets become solvable. We investigate the complexity of decision procedures for these problems and show by reducing a bounded version of Hilbert's Tenth Problem to the finite containment problem that these two problems are extremely hard, that, in fact, the complexity of each decision procedure exceeds any primitive recursive function infinitely often.

A Simple and Flexible System Initialization Mechanism

2023-03-30T04:01:01Z

A Simple and Flexible System Initialization Mechanism Luniewski, Allen W. This thesis presents an approach to system initialization which is simple and easy to understand and, at the same time, is versatile in the face of configuration changes. This thesis considers initialization of a layered system. The initialization mechanism is built upon three key concepts: existence of a minimal configuration, a core image of the system and dynamic reconfiguration.

Non-discretionary Access Control for Decentralized Computing Systems

2023-03-30T03:36:01Z

Non-discretionary Access Control for Decentralized Computing Systems Karger, Paul A. This thesis examines the issues relating to non-discretionary access controls for decentralized computing systems. Decentralization changes the basic character of a computing system from a set of processes referencing a data base to a set of processes sending and receiving messages. Because massages must be acknowledge, operations that were read-only in a centralized system become read-write operations.

A Layered Virtual Memory Manager

2023-03-30T03:21:10Z

A Layered Virtual Memory Manager Mason, Andrew Halstead This thesis presents a specification for the Multics virtual memory manager. The virtual memory manager is that part of the operating system which coordinates the usage of physical memory and which manages the bindings between logical memory and physical memory. In the case of Multics, physical memory is composed of fixed-length blocks called frames and logical memory consists of segments, representing sets of frames.

A Digitalis Therapy Advisor with Explanations

2023-03-30T03:40:19Z

A Digitalis Therapy Advisor with Explanations Swartout, William R. This thesis describes the English explanation facility of the OWL Digitalis Advisor, a program designed to advise physicians regarding digitalis therapy. The program is written in OWL, an English-based computer language being developed at MIT. The system can explain, in English, both the methods it uses and how those methods were applied during a particular session. In addition, the program can explain how it acquires information and tell the user how it deals with that information either in general or during a particular session.

A Robust Environment for Program Development

2023-03-30T03:04:51Z

A Robust Environment for Program Development Goldberg, Harold J. This thesis examines the problems of debugging and preservation of the user programming environment and proposes a scheme by which the program development environment can be protected. Typically, designers of timeshared or multiprogrammed computer systems only consider inter-user interference as a source of problems and do not worry about what users do in their own environments. Thus, users can, by writing incorrect programs, cause destruction of the programming environment and personal data bases.

A Case Study of Intermodule Dependencies in a Virtual Memory Subsystem

2023-03-30T04:01:53Z

A Case Study of Intermodule Dependencies in a Virtual Memory Subsystem Hunt, Douglas H. A problem currently confronting computer scientists is to develop a method for the production of large software systems that are easy to understand and certify. The most promising methods involve decomposing a system into small modules in such a way that there are few intermodule dependencies.

Coordination of Parallel Processes in the Actor Model of Computation

2023-03-30T03:35:03Z

Coordination of Parallel Processes in the Actor Model of Computation Goodman, Nathan Two algorithms for the mutual exclusion problem are described and proven to operate correctly. The algorithms are unique in that they use very simple synchronization primitives yet are fair and retain their fairness even if the number of parallel processes in the computer system increases unboundedly over time. One of the algorithms uses simple cells of read/write storage as the primitive; the algorithm is similar to the classic algorithms for this problem proposed by Dijkstra and Knuth, but is generalized to handle an arbitrary number of processes.

A Multi-process Design of Paging System

2023-03-30T03:09:53Z

A Multi-process Design of Paging System Huber, Andrew R. This thesis presents a design for a paging system that may be used to implement a virtual memory on a large scale, demand paged computer utility. A model for such a computer system with a multi-level, hierarchical memory system is presented. The functional requirements of a paging system for such a model are discussed, with emphasis on the parallelism inherent in the algorithms used to implement the memory management functions.

The Logic of Systems

2023-03-30T03:56:13Z

The Logic of Systems Furtek, Frederick Curtis We present a theory about the logical relationships associated with system behavior. The rules governing the behavior of a system are expressed by a Petri net. A set of assumptions about the modeling of a system permit us to separate system behavior into two components, what we refer to as information and control.

Diagnostic Planning and Cancer Management

2023-03-30T03:18:59Z

Diagnostic Planning and Cancer Management Safran, Charles; Desforges, Jane F.; Tsichlis, Philip N. This report describes a computer system for evaluating patients with Hodgkin's disease which has been developed by Clinical Decision Making Group (CDMG) at MIT Laboratory for Computer Science in conjunction with the Blood Research Laboratory of the New England Medical Center Hospitals and Department of Hematology, Tufts University School of Medicine (T-NEMC.H.). This system uses decision theoretic techniques to aid in the formulation of a diagnostic plan for cancer patient.

Semantical Considerations on Floyd-Hoare Logic

2023-03-30T03:13:21Z

Semantical Considerations on Floyd-Hoare Logic Pratt, Vaughan R. This paper deals with logics of programs. The objective is to formalize a notion of program description and to give both plausible (semantic) and effective (syntactic) criteria for the notion of truth of a description. A novel feature of this treatment is the development of the mathematics underlying Floyed-Hoare axiom systems independently of such systems. Our directions that such research might take are also considered.

Using Type Extension to Organize Virtual Memory Mechanisms

2023-03-30T03:03:22Z

Using Type Extension to Organize Virtual Memory Mechanisms Janson, Philippe Arnaud Much effort is currently being devoted to producing systems that are easy to understand, to verify and to develop. The general methodology for designing such a system consists of decomposing it into a structured set of modules so that the modules can be understood, verified and developed individually, and so that the understanding/ verification of the system can be derived from the understanding/ verification of its modules. while many of the mechanisms in a computer system have been decomposed successfully into a structured set of modules, no technique has been proposed to organize the virtual memory mechanism of a system in such a way.

Index Selection in a Self-Adaptive Relational Data Base Management System

2023-03-30T03:19:10Z

Index Selection in a Self-Adaptive Relational Data Base Management System Chan, Arvola Y. The development of large integrated data bases that support a variety of applications in an enterprise promises to be one of the most important data processing activities of the next decade. The effective utilization o such data bases depends on the ability of data base management systems to cope with the evolution of data base applications.

High Level Expression of Semantic Integrity Specifications in a Relational Data Base System

2023-03-30T03:53:12Z

High Level Expression of Semantic Integrity Specifications in a Relational Data Base System McLeod, Dennis J. The "semantic integrity" of a data base is said to be violated when the data base ceases to represent a legitimate configuration of the application environment it is intended to model. In the context of the relational data model, it is possible to identify multiple levels of semantic integrity information: (1) the description of the domains of the data base, as abstract sets of atomic data values (domain definition), (2) the specification of the fundamental structure of the data (relation structure specification), (3) the definition of the abstract operations which are meaningful in terms of the application environment (structured operations), and (4) the expression of additional semantic information not contained in the structure of the relations nor in the identities of their underlying domains (relation constraints).

Processor Multiplexing in a Layered Operating Systems

2023-03-30T03:40:32Z

Processor Multiplexing in a Layered Operating Systems Reed, David Patrick This thesis presents a simply structured design for the implementation of process in a kernel-structured operating system. The design provides a minimal mechanism for the support of two distinct classes of processes found in the computer system -- those which are part of kernel operating system itself, and those used to execute user-specified computations.

A Secure and Flexible Model of Process Initiation for a Computer Utility

2023-03-30T04:14:14Z

A Secure and Flexible Model of Process Initiation for a Computer Utility Montgomery, Warren Alan This thesis demonstrates that the amount of protected, privileged code related to process initiation in a computer utility can be greatly reduced by making process creation unprivileged. The creation of processes can be controlled by the standard mechanism for controlling entry to a domain, which forces a new process to begin execution at a controlled location.

Encryption-based Protection Protocols for Interactive User-computer Communication

2023-03-30T03:46:38Z

Encryption-based Protection Protocols for Interactive User-computer Communication Kent, Stephen T. This thesis develops a complete set of protocols, which utilize a block cipher, e.g., the NBS data encryption standard, for protection interactive user-computer communication over physically unsecured channels. The use of the block cipher protects against disclosure of message contents to an intruder, and the protocols provide for the detection of message stream modification and dental of message service by an intruder.

Decidability Questions for Petri Nets

2023-03-30T03:53:25Z

Decidability Questions for Petri Nets Hack, Michel Henri Théodore An understanding of the mathematical properties of Petri Nets is essential when one wishes to use Petri Nets as an abstract model for concurrent systems. The decidability of various problems which arise in this context is an important aspect of this question. The fact that these problems also arise in the context of other mathematical theories, such as commutative, closure under linear relations, Matrix Context-Free grammars, or Weak Counter Automata, provides further motivation.

A Program for the Design of Procurement Systems

2023-03-30T04:01:07Z

A Program for the Design of Procurement Systems Bosyj, Michael Computer technology has had a limited success in producing useful business applications. Management systems seldom meet users' requirements, are often inappropriate to an application, and are frequently abandoned. But why? Business lacks expertise in the application of computers .

Petri Net Language

2023-03-30T03:39:50Z

Petri Net Language Hack, Michel Henri Théodore In a labeled Petri Net we assign symbols from an alphabet to some or all the transitions of a Petri Net. To each firing sequence of such a Labeled Petri Net corresponds to a string over the alphabet. We study the languages obtained in this way by all firing sequences of a Petri Net, or by all firing sequences which reach a given final marking.

Some Data Base Applications of Constraint Expressions

2023-03-30T03:13:35Z

Some Data Base Applications of Constraint Expressions Grossman, Richard Weaver This report presents a novel network-like representation for information, called "constraint expressions" (CE). CE makes use of some of the knowledge-representation techniques developed by Artificial Intelligence research.

A Preliminary Study in Computer-aided Legal Analysis

2023-03-30T03:43:14Z

A Preliminary Study in Computer-aided Legal Analysis Meldman, Jeffrey A. This paper describes the prototype for a computer system that can perform a simple kind of legal analysis. The system user, who is presumed to be a lawyer, describes to the system a hypothetical set of facts. The system determines the extent to which these facts fall within certain legal doctrines (by syllogism), or near to these doctrines (by analogy).

Minimizing the Naming Facilities Requiring Protection in a Computing Utility

2023-03-30T03:52:06Z

Minimizing the Naming Facilities Requiring Protection in a Computing Utility Bratt, Richard Glenn This thesis examines the various mechanisms for naming the information objects stored in a general-purpose computing utility, and isolates a basic set of naming facilities that must be protected to assure complete control over user interaction and that allow desired interactions among users to occur in a natural way. Minimizing the protected naming facilities consistent with functional objective of controlled, but natural, user interaction contribute to defining a security kernel for a general-purpose computing utility.

Mechanization of Temporal Knowledge

2023-03-30T04:22:45Z

Mechanization of Temporal Knowledge Kahn, Kenneth M. The design and implementation of a collection of computer programs knowledgeable about time "in general," called the time specialist, is described. The thesis that this time specialist can be placed in the service of larger more general problem solvers is demonstrated for two examples, medical diagnosis and the understanding of a time-travel story.

Semantic of Communication Parallel Processes

2023-03-30T04:10:59Z

Semantic of Communication Parallel Processes Greif, Irene Gloria The thesis of this dissertation is that an understanding of the ordering constraints that are introduced among events of parallel process is essential to the understanding of synchronization and that therefore any language for specifying synchronization of parallel processes should be based on a theory of such orderings. While it is possible to write specifications for systems communicating parallel processes by reference to the time ordering of some global clock external to the system, such specifications cannot be as useful as ones which are in terms of orderings derivable within the system.

Strategy Selection in Medical Diagnosis

2023-03-30T03:44:29Z

Strategy Selection in Medical Diagnosis Miller, Peter B. The recorded, verbal problem-solving behavior of doctors performing the diagnostic task of taking a present illness was analyzed in this research. The goal of the analysis was to discover that data-acquisition strategies were used by the doctors to accomplish the task. A model called the strategy frame model was created to describe the strategies that were found and to provide a mechanism for the selection of a strategy.

Equivalence Problems for Monadic Schemas

2023-03-30T03:49:23Z

Equivalence Problems for Monadic Schemas Qualitz, Joseph E. A class of monadic program schemas is defined. This class, called iteration schemas, consists of schemas whose programs comprise assignment statements, conditional statements, and iteration statements. These schemas are shown to correspond to program schemas which are structured, and are shown to be strictly less "powerful" than monadic program schemas.

Automatic Test, Configuration and Repair of Cellular Arrays

2023-03-30T03:01:03Z

Automatic Test, Configuration and Repair of Cellular Arrays Manning, Frank B. A cellular array is an iterative array of identical information processing machines, cells. The arrays discussed are rectangular arrays of programmable logic, in which information stored in a working cell tells the cell how to behave. No signal line connects more than a few cells. A loading mechanism in each cell allows a computer directly connected to one cell to load any good cell that is not walled off by flawed cells.

A Portable Compiler for the Language C

2023-03-30T03:23:19Z

A Portable Compiler for the Language C Snyder, Alan This paper describes the implementation of a compiler for the language C. The compiler has been designed to be able to be capable of producing assembly-language code for most register-oriented machines with only minor recoding.

Program Restructuring for Virtual Memory Systems

2023-03-30T03:14:29Z

Program Restructuring for Virtual Memory Systems Johnson, Jerry William The problem area addressed in this report is program restructuring, a method of reordering the relocatable sectors of a program in its address space to increase the locality of the programs reference behavior, thereby reducing the number of page fetches require for execution in a virtual memory system.

A Formalization and Correctness Proof of the CGOL Language System

2023-03-30T03:41:50Z

A Formalization and Correctness Proof of the CGOL Language System VanDeVanter, Michael Lee In many important ways the design and implementation of programming languages are hindered rather than helped by BNF. We present an alternative meta-language based on the work of Pratt which retains much of the effective power of BNF but is more convenient for designer, implementer, and user alike. Its amenability to formal treatment is demonstrated by a rigorous correctness proof of a simple implementation.

The Computational Complexity of Some Logical Theories

2023-03-30T04:13:56Z

The Computational Complexity of Some Logical Theories Rackoff, Charles Weill Upper and lower bounds on the inherent computational complexity of the decision problem for a number of logical theories are established. A general form of Ehrenfeucht game technique for deciding theories is developed which involves analyzing the expressive power of formulas with given quantifier depth. The method allows one to decide the truth of sentences by limiting quantifiers to range over finite sets.

A Digitalis Therapy Advisory

2023-03-30T03:04:43Z

A Digitalis Therapy Advisory Silverman, Howard The physician administering digitalis makes use of the full richness of the clinical setting to form his/her impressions and decide on a therapeutic program. The weakness of existing programs which formulate digitalis dosage regimens lies in their inability to use all of the clinical data available-both quantitative. and qualitative. This report describes the construction of a computer system which formulates digitalis dosage regimens and which adjusts this regimen by interpreting the patient's response to the original dosage regimen.

Some Problems in German in English Machine Translation

2023-03-30T03:41:03Z

Some Problems in German in English Machine Translation Brown, Gretchen P. This paper discusses some problems in the machine translation of natural language, in particular, for translation from German into English. An implementation of some parts of the translating process has been built. The system consists of a German interpretive grammar, to take in German text and output a set of semantic representation, and a generator, to produce English sentences from single semantic representations.

Naming and Protection in Extendable Operating Systems

2023-04-07T18:24:22Z

Naming and Protection in Extendable Operating Systems Redell, David D. The properties of capability-based extendible operating systems are described, and various aspects of such systems are discussed, with emphasis on the conflict between free distribution of access privileges and later revocation of those privileges.

Nondeterministic Time and Space Complexity Classes

2023-03-30T04:19:19Z

Nondeterministic Time and Space Complexity Classes Seiferas, Joel Irvin The marginal utility of the Turing machine computational resources running time and storage space are studied. A technique is developed which, unlike diagonalization, applies equally well to nondeterministic and deterministic automata. For f, g time or space bounding functions with f (n+1) small compared to g(n), it is shown that, in terms of word length n, there are languages which are accepted by Turing machines operating within time or space g(n) but which are accepted by no Turing machine operating within time or space f(n). The proof involves use of the recursion theorem together with "padding" or "translational" techniques of formal language theory.

Functional Domains of Applicative Languages

2023-03-30T03:55:51Z

Functional Domains of Applicative Languages Ward, Stephen A. The expressive power of a particular applicative language may be characterized by the set of abstract functions directly representable in that language. The common FUNARG and applicative order problems are scrutinized in this way, and the effects of these weaknesses are related to the inexpressibility of classes of functions.

Semantics of Data Structures and References

2023-03-30T03:14:38Z

Semantics of Data Structures and References Ellis, David J. Each programming language that handles data structures has its own set of rules for working with them. Notions such as assignment and construction of structures values appear in a huge number of different and complicated versions. This thesis presents a methodology which provides a common basis for describing ways in which programming languages deal with data structures and reference to them.

Removing the Dynamic Linker from the Security Kernel of a Computing Utility

2023-03-30T03:41:34Z

Removing the Dynamic Linker from the Security Kernel of a Computing Utility Jason, Philippe Arnaud In order to enforce the security of the information stored in a computing utility, it is necessary to certify that the protection mechanism is correctly implemented so that there exist no uncontrolled access path to the stored information.

Mathematical Logic for Computer Scientists

2023-03-30T03:01:37Z

Mathematical Logic for Computer Scientists Levin, Michael This book is an introductory course in mathematical logic covering basic topics in quantification theory and recursive function theory, and is intended for the reader who is interested in artificial intelligence, computer linguistics, and other related areas. The text is theoretical, but organized with implementation in mind.

Using Interactive Graphics in Simulating the Hospital Emergency Room

2023-03-30T03:55:48Z

Using Interactive Graphics in Simulating the Hospital Emergency Room Weissberg, Richard W. The hospital emergency room is a complex system having many interrelated factors contributing to its operation. The emergency room administrator has limited control over certain of these factors: numbers of beds, nurses, doctors, x-ray units; for example. Other factors such as patient arrival rates and demands made upon available resources are largely uncontrollable.

The Computer Utility as a Marketplace for Computer Service

2023-03-30T04:04:51Z

The Computer Utility as a Marketplace for Computer Service Frankston, Robert Mm. Computers are unique in their ability to be programmed for a wide variety of applications. This is in contrast with hardware dedicated to specific tasks such as the telephone system. Because of its flexibility, a computer system can support, concurrently, many diverse services that do not require dedicated hardware.

An Experimental Analysis of Program Reference Patterns in the Multics Virtual Memory

2023-03-30T04:17:09Z

An Experimental Analysis of Program Reference Patterns in the Multics Virtual Memory Greenberg, Bernard Stewart This thesis reports the design, conducting, and results of an experiment intended to measure the paging rate of a virtual memory computer system as a function of paging memory size. This experiment, conducted on the Multics computer system at MIT, a large interactive computer utility serving an academic community, sought to predict paging rates for paging memory sizes larger than existing memory at the time.

A Model-debugging System

2023-03-30T04:00:11Z

A Model-debugging System Mark, William S.

Verification of Programs Operating on Structured Data

2023-03-30T04:07:41Z

Verification of Programs Operating on Structured Data Laventhal, Mark Steven The major method for verifying the correctness of computer program is the inductive assertion approach. This approach has been limited in the past by the lack of techniques for handling data structures. In particular, there has been a need for concepts with which to describe structured data during intermediate and final stages of a computation.

Introduction to Multics

2023-03-30T03:21:48Z

Introduction to Multics Saltzer, Jerome H. The Multics project was begun in 1964 by the Computer Systems Research group of M.I.T. Project MAC. The goal was to create a prototype of a computer utility. In 1965, the project became a cooperative venture of M.I.T. Project MAC, the General Electric Company Computer Department (now Honeywell Information Systems Inc. ) and Bell Telephone Laboratories. In 1969, at the end of the research phase of the project, Bell Telephone Laboratories ended its active involvement.

On Lower Bounds for Selection Problems

2023-03-30T04:02:19Z

On Lower Bounds for Selection Problems Yao, Foong Frances Let V i (n) be the minimum number of binary comparisons that are required to determine the i-th largest of n elements drawn from a totally ordered set. In this thesis we use adversary strategies to prove lower bounds on V i (n). For i = 3, our lower bounds determine V 3(n) precisely for infinitely many values of n,and determine V 3(n) to within 2 for all n.

Analysis of Asynchronous Concurrent Systems by Timed Petri Nets

2023-04-07T18:17:49Z

Analysis of Asynchronous Concurrent Systems by Timed Petri Nets Ramchandani, Chander This thesis is concerned with the modeling and performance analysis of systems which consist of concurrently acting components, an example of which is an asynchronous pipelined processor. The work is divided into two parts. In the first part, a suitable model is developed for describing the structure of asynchronous concurrent systems. In conventional automata theory, the finite-state machine model is used to describe the behavior of systems; the problem with this is that a large number of states results when practical systems are modelled.

An Abstract Model of a Research Institute: Simple Automatic Programming Approach

2023-03-30T04:05:26Z

An Abstract Model of a Research Institute: Simple Automatic Programming Approach Briabrin, Victor A problem of knowledge representation is considered in terms of designing a model for a simple sociological structure. A version of the access language is proposed which is based on three kind of expressions accepted by the system - constructors, specificators and requests. In addition, some topics concerned with model implementation and extension are discussed.

An Input/Output Architecture for Virtual Memory Computer Systems

2026-02-05T21:18:16Z

An Input/Output Architecture for Virtual Memory Computer Systems Clark, David D In many large systems today, input/output is not performed directly by the user, but is done interpretively by the system for him, which causes additional overhead and also restricts the user to whatever algorithms the system has implemented. Many causes contribute to this involvement of the system in user input/output, including the need to enforce protection requirements, the inability to provide adequate response to control signals from devices, and the difficulty of running devices in a virtual environment, especially a virtual memory.

Backup and Recovery of On-line Information in a Computer Utility

2023-03-30T03:39:32Z

Backup and Recovery of On-line Information in a Computer Utility Stern, Jerry A. This thesis describes a design for an automatic backup mechanism to be incorporated in a computer utility for the protection of on-line information against accidental or malicious destruction. This protection is achieved by preserving on magnetic tape recent copies of all items of information known to the online system. In the event of a system failure, file system damage is automatically assessed and missing information is recovered from backup storage.

Packet Communication

2023-03-30T03:07:54Z

Packet Communication Metcalfe, Robert Melancton This report develops a theory of packet communication; it analyzes users of computers in digital communication systems and examines structures for organizing computers in highly communicative environments. Various examples from existing computer networks, including the ARPA Computer Network and the ALOHA System, are used to motivate and substantiate analysis of (1) store-and-forward packet communication, (2) broadcast packet communication, and (3) distributed interprocess communication.

On Reducibility Among Combinatorial Problems

2023-03-30T03:35:42Z

On Reducibility Among Combinatorial Problems Herrmann, Paul Peter A large class of combinatorial problems have been shown by Cook and Karp to be computationally equivalent to within a polynomial. We exhibit some new problems in this class, and provide simpler proofs for some of the known reductions.

Productivity in Parallel Computational Schemata

2023-03-30T04:07:16Z

Productivity in Parallel Computational Schemata Linderman, John P. A general model for parallel computation is developed in three parts. One part, the data flow graph, describes how actors which transform and test values are connected to the locations in a finite memory. Another part, an interpretation, supplies information about the contents of memory and the detailed nature of the transformations and tests.

Complexity Classes of Recursive Functions

2023-03-30T03:13:24Z

Complexity Classes of Recursive Functions Moll, Robert An honest function is one whose size honestly reflects its computation time. In 1969 Meyer and McCreight proved the "honesty theorem," which says that for every t, the t-computable functions are the same as the t'computable functions for some honest honest t'.

Storage Hierarchy Systems

2023-03-30T04:21:27Z

Storage Hierarchy Systems Madnick, Stuart E. The relationship between page size, program behavior, and page fetch frequency in storage hierarchy systems is formalized and analyzed. It is proven that there exist cyclic program reference patterns that can cause page fetch frequency to increase significantly if the page used is decreased (e.g., reduced by half).

The Emptiness and Complementation Problems for Automata on Infinite Trees

2023-03-30T04:06:40Z

The Emptiness and Complementation Problems for Automata on Infinite Trees Rackoff, Charles Weill In [6] Rabin defines Automata on Infinite Trees, and the body of that paper is concerned with proving two theorems about these automata. The result we consider in the first chapter says that there exists an effective procedure to determine, given an automaton on infinite trees, whether or not it accepts anything at all. We present a new decision procedure which is much simpler than Rabin's since we do not use an induction argument as he does.

An Analysis of Sorting Networks

2023-03-30T03:33:54Z

An Analysis of Sorting Networks Smith, Burton J. Comparators which sort two numbers can be interconnected to form networks which sort n numbers for any n. The input and output characteristics of comparator networks are analyzed from several different points of view.

Cooperation of Mutually Suspicious Subsystems in a Computer Utility

2023-03-30T04:27:17Z

Cooperation of Mutually Suspicious Subsystems in a Computer Utility Schroeder, Michael D. This thesis describes practical protection mechanisms that allow mutually suspicious subsystems to cooperate in a single computation and still be protected from one another. The mechanisms are based on the division of a computation into independent domains of access privilege, each of which may encapsulate a protected subsystem. The central component of the mechanisms is a hardware processor that automatically enforces the access constraints associated with a multidomain computation implemented as a single execution point in a segmented virtual memory.

Finite Tree Automata and W-Automata

2023-04-07T18:09:13Z

Finite Tree Automata and W-Automata Hossley, Robert Chapter I is a survey of finite automata as acceptors of finite labeled trees. Chapter II is a survey of finite automata as acceptors of infinite strings on a finite alphabet. Among the automata models considered in Chapter II are those used by McNaughton, Buchi, and Landweber. In Chapter II we also consider several new automata models based on a notion of a run of a finite automataton on an infinite string suggested by Professor A.R. Meyer in private communication. We show that these new models are all equivalent to various previously formulated models.

On the Design and Specification of a Common Base Lanaguage

2023-03-30T03:50:04Z

On the Design and Specification of a Common Base Lanaguage Dennis, Jack B. This is the report on the work of the Computational Structures Group of Project MAC toward the design and specification of a common base language for programs and information structures. We envision that the meanings of programs expressed in practical source languages will be defined by rules of translation into the base language.

Further Results on Hierarchies of Canonic Systems

2023-03-30T03:39:09Z

Further Results on Hierarchies of Canonic Systems Mandl, Robert This thesis outlines a new way of presenting the theory of canonic systems, including a distinction (for mathodic reasons) between simple canonic systems and general canonic systems, and proves a series of results on hierarchies of canonic systems. After a brief summary of Doyle's results on a partial hierarchy of canonic systems, a new hierarchy is developed (Chapter II) which relates the general canonic systems not only to all 4 types of formal grammars defined by Chomsky but also to any class shown (Chapter III) that all attempts to define a mathematical system which exactly corresponds to the recursive sets are necessarily fruitless.

Relativization of the Theory of Computational Complexity

2023-03-30T03:15:33Z

Relativization of the Theory of Computational Complexity Lynch, Nancy A. Blum's machine-independent treatment of the complexity of partial recursive functions is extended to relative algorithms (as represented by Turing machines with oracles). We prove relativizations of several results of Blum complexity theory, such as the compression theorem. A recursive relatedness theorem is proved, showing that any two relative complexity measures are related by fixed recursive function. This theorem allows us to obtain proofs of results for all measures from proofs for a particular measure.

The Complexity of Finite Functions

2023-03-30T04:08:36Z

The Complexity of Finite Functions Vilfan, Bostjan Lower bounds on the length of formulas for finite functions are obtained from a generalization of a theorem of Specker. Let f: (0,1,...,d-1) [0,1,...,d-1] be a function which can be represented by a formula of length < c.n. For any m, if n is sufficiently large, there is a restriction f': {0,1,...,d-1}m > {0,...,d-1} of f which, is representable by special class of formulas called homogeneous e-complexes.

Autonomous, Synchronous Counters Constructed Only of J-K Flip-flops

2023-03-30T03:02:49Z

Autonomous, Synchronous Counters Constructed Only of J-K Flip-flops Manning, Frank This report describes research into some properties of autonomous, synchronous counters constructed with only the simplest form of J-K Flip-Flop. The research revolved around a system with a special-purpose digital machine and a general-purpose computer. The special-purpose searched through all the possible counters constructed of five or fewer J-K Flip-Flops for all counters with a period equal to that specified by th input to the system.

Essays in Algebraic Simplification

2023-03-30T03:11:56Z

Essays in Algebraic Simplification Fateman, Richard J. This thesis consists of essays on several aspects of the problem of algebraic simplification by computer. Since simplification is at the core of most algebraic manipulations, efficient and effective simplification procedures are essential to building useful computer systems for non-numerical mathematics. Efficiency is attained through carefully designed and engineered algorithms, heuristics,and data types, while effectiveness is assured through theoretical considerations.

Analysis of Production Schemata by Petri Nets

2023-03-30T03:45:20Z

Analysis of Production Schemata by Petri Nets Hack, Michel Henri Théodore Petri nets provide a powerful graphical tool for representing and analyzing complex concurrent systems. Properties such as hang-up freeness, determinacy, conflict, concurrency and dependency, can be represented and studied. The precise relationship between structural and behavioral properties, and between local and global properties is not well-understood for the most general class of Petri Nets.

Induction in Proofs about Programs

2023-03-30T03:17:50Z

Induction in Proofs about Programs Greif, Irene Gloria Four methods for proving equivalence of programs by induction are described and compared. They are recursion induction, structural induction, mu-rule induction, and truncation induction. McCarthy's formalism for conditional expressions as function definitions is used and reinterpreted in view of Park's work on results on results in lattice theory as related to proofs about programs. The possible application of this work to automatic program verification is commented upon.

Evaluation of Definite Integrals by Symbolic Manipulation

2023-03-30T03:02:58Z

Evaluation of Definite Integrals by Symbolic Manipulation Wang, Paul S. A heuristic computer program for the evaluation of real definite integrals of elementary functions is described. This program, called WANDERER (WANg's DEfinite integRal EvaluatoR), evaluates many proper and improper integrals. The improper integrals may have a finite or infinite range of integration. Evaluation by contour integration and residue theory is among the methods used. A program called DELIMITER (DEfinitive LIMITEvaluatoR) is used for the limit computations needed in evaluating some definite integrals.

Cost Analysis of Debugging Systems

2023-03-30T04:26:57Z

Cost Analysis of Debugging Systems Lester, Bruce P. A general method is presented for performing cost analysis of interactive debugging systems. The method is based on an abstract model of program execution. This model is derived from the interpreter used in the Vienna method of semantic definition of PL/I. A brief discussion of the overall operation and significance of Vienna interpreter is included.

Primary Access Control in Large-scale Time-shared Decision Systems

2023-03-30T04:02:37Z

Primary Access Control in Large-scale Time-shared Decision Systems Owens, Richard C., Jr. The computer differs from other tools in that it presently does not provide its users with a working environment transparent to their desires; in particular, current computer systems do not support adequate mechanisms for controlled sharing of sensitive information. Four primary dimensions of the access control problem are identified. They are: 1) the physical level at which to apply control; 2) the fineness of distinction applied to the term ""access"" 3) the meaning of the term "user identification",and 4) the degree of sophistication employed in automatically assigned restrictions to new data files.

Bounds on Information Retrieval Efficiency in Static File Structures

2023-03-30T03:45:13Z

Bounds on Information Retrieval Efficiency in Static File Structures Welch, Terry A. This research addresses the problem of file organization for efficient information retrieval when each file item may be accessed through any one of a large number of identification keys. The emphasis is on library problems, namely large, low-update, directory-oriented files, but other types of files are discussed.

Dynamic Reconfiguration in a Modular Computer System

2023-03-30T03:29:35Z

Dynamic Reconfiguration in a Modular Computer System Schell, Roger R. This thesis presents an orderly design approach for dynamically changing the configuration of constituent physical units in a modular computer system. Dynamic reconfiguration contributes to high system availability by allowing preventative maintenance, development of new operating systems, and changes in system capacity on a non-interference basis.

Automatic Creation of a Code Generator from a Machine Description

2023-03-30T03:42:58Z

Automatic Creation of a Code Generator from a Machine Description Miller, Perry L. This paper studies some of the problems involved in attaining machine independence for a code generator, similar to the language independence and the token independence attained by automatic parsing and automatic lexical systems. In particular, the paper examines the logic involved in two areas of code generation: computation and data reference.

Computer Analysis of Visual Properties of Curved Objects

2023-03-30T04:16:08Z

Computer Analysis of Visual Properties of Curved Objects Krakauer, Lawrence J. A method is presented for the visual analysis of objects by computer. It is particularly well suited for opaque objects with smoothly curved surfaces. The method extracts information about the object's surface properties, including measures of its specularity, texture, and regularity. It also aids in determining the object's shape.

Information Processing and Transmission in Cellular Automata

2023-03-30T03:46:07Z

Information Processing and Transmission in Cellular Automata Banks, Edwin R. A cellular automaton is an iterative array of very simple identical information processing machines called cells. Each cell can communicate with neighboring cells. At discrete moments of time the cells can change from one state to another as a function of the states of the cell and its neighbors. Thus on a global basis, the collection of cells is characterized by some type of behavior.

Shape from Shading: A Method for Obtaining the Shape of a Smooth Opaque Object From One View

2023-03-30T03:01:39Z

Shape from Shading: A Method for Obtaining the Shape of a Smooth Opaque Object From One View Horn, Berthold K. P. A method will be described for finding the shape of a smooth opaque object from a monocular image, given a knowledge of the surface photometry, the position of the light-source and certain auxiliary information to resolve ambiguities. This method is complementary to the use of stereoscopy which relies on matching up sharp detail and will fail on smooth objects. Until now the image processing of a single views has been restricted to objects which can meaningfully be considered two-dimensional or bounded by plane surfaces.

Design Strategies for File Systems

2023-03-30T04:24:13Z

Design Strategies for File Systems Madnick, S.E. This thesis describes a methodology for the analysis and synthesis of modern general purpose file systems. The two basic concepts developed are (1) establishment of a uniform representation of a file's structure in the form of virtual memory or segmentation and (2) determination of a hierarchy of logical transformations within a file system.

Complexity Measures for Language Recognition by Canonic Systems

2023-03-30T04:11:49Z

Complexity Measures for Language Recognition by Canonic Systems Haggerty, Joseph P. A canonic system C is a specification of a recursively enumerable set, such as a set of strings over a finite alphabet. From this description C, it is possible to generate a system C , called a proof measure function, which is an indication of the complexity of the language defined. For certain simple but important classes of canonic system, algebraic bounds on these functions can be derived from the structure of the system.

Deadlock-free Sharing of Resources in Asynchornous Systems

2023-03-30T03:36:47Z

Deadlock-free Sharing of Resources in Asynchornous Systems Hebalkar, Prakash G. Whenever resources are shared among several activities that hoard resources, the activities can attain a state of deadlock in which, for lack of resources, none of the activities can proceed. Deadlocks can be prevented by coordination of the sharing. efficient running of the activities under such coordination requires knowledge of the patterns of use of resources by the activities.

Integral Convex Polyhedra and an Approach to Integralization

2023-03-30T04:04:20Z

Integral Convex Polyhedra and an Approach to Integralization Edelberg, Murray Many combinatorial optimization problems may be formulated as integer linear programming problems - that is, problems of the form: given a convex polyhedron P contained in the non-negative orthant of n-dimensional space, find a integer point in P which maximizes (or minimizes) a given linear objective function. Well known linear programming methods would suffice to solve such a problem if: (i) P is an integral convex polyhedron, or (ii) P is transformed into the integral convex polyhedron that is the convex hull of the set of integer points in P, a process which is called integralization.

Computer Recognition of Prismatic Solids

2023-03-30T03:00:53Z

Computer Recognition of Prismatic Solids Griffith, Arnold Koons An investigation is made into the problem of constructing a model of the appearance to an optical input device of scenes consisting of plane-faced geometric solids. The goal is to study algorithms which find the real straight edges in the scenes, taking into account smooth variations in intensity over faces of the solids, blurring of edges and noise.

Coordination of Asynchronous Event

2023-03-30T03:51:43Z

Coordination of Asynchronous Event Patil, Suhas Shrikrishna The way activity in a system proceeds is that events occur as a result of some conditions and lead to some new conditions which make other events possible. Often it is necessary to coordinate such events to ensure proper behavior. Coordination nets for representing such coordinations and physically realizable structures for enforcing such coordinations are presented. These structures are modular and can be mechanically derived from the coordination nets. Coordination involved in concurrent management of resources are also discussed.

A Computer-controlled Graphical Display Processor

2023-03-30T03:50:08Z

A Computer-controlled Graphical Display Processor Fiasconaro, James Gerard A cathode-ray tube, (CRT), is frequently employed to display text and drawings generated by a digital computer. Unfortunately, all of the commercially available CRT display systems are either very expensive or have limited dynamic capability resulting from the use of some form of storage-type CRT. A need exists to develop a low-cost, relatively sophisticated display compute-generated pictures.

Generalized Organization of Large Data Bases: A Set-theoretic Approach to Relations

2023-03-30T04:21:32Z

Generalized Organization of Large Data Bases: A Set-theoretic Approach to Relations Fillat, Andrew Irwin; Kraning, Leslie Alan Problems inherent in representation and manipulation of large data bases are discussed. Data management is considered as the manipulation of relationships among elements of a data base. A detailed analogy introduces concepts embodied in a data management system. Set theory is used to describe a model for data-bases, and operations suitable for manipulation of relations are defined.

Economies of Scale in Computer Use: Initial Test and Implication A for the Computer Utility

2023-03-30T03:11:13Z

Economies of Scale in Computer Use: Initial Test and Implication A for the Computer Utility Selwyn, Lee L. This study is concerned with the existence of economies of scale in the production of data processing and other computing services, and the possible regulatory and public policy implications of such economies. The rapid development of the technology of computation since the Second World War has raised many questions as to the supervision by public authorities of the use and progress of this technology.

Controlled Information Sharing in a Computer Utility

2023-03-30T03:38:32Z

Controlled Information Sharing in a Computer Utility Vanderbilt, Dean H. A computer utility is envisioned as a large, multi-access computer system providing its users with the ability to store information and share its use with other system users. This thesis considers the nature of information sharing and how a computer utility can provide facilities allowing such sharing to take place in a controlled manner.

Recognition of Translators Invariants* By Iterative Arrays

2023-04-07T17:44:14Z

Recognition of Translators Invariants* By Iterative Arrays Beyer, Wendel Terry A study is made of the recognition and transformation of figures by iterative arrays of finite state automata. A figure is a finite rectangular two-dimensional array of symbols. The iterative arrays considered are also finite, rectangular and two-dimensional.

Practical Translators for LR(k) Languages

2023-03-30T04:21:10Z

Practical Translators for LR(k) Languages Deremer, Franklin Lewis A context-free syntactical translator (CFST) is a machine which defines a translation from one context-free language to another. A transduction grammar is a formal system based on a context-free grammar and it specifies a context-free syntactical translation. A simple suffix transduction grammar based on a context-free grammar which is LR(k) specifies a translation which can be defined by a deterministic push-down automation (DPDA).

A Graph Model for Parallel Computations

2023-03-30T03:08:53Z

A Graph Model for Parallel Computations Rodrigues, Jorge E. This report presents a computational model called program graphs which makes possible a precise description of parallel computations of arbitrary complexity on non-structured data. In the model, the computation steps are represented by the nodes of a directed graph whose links represent elements of storage and transmission of data and /or control information.

Case Study in Interactive Graphics Programming: A Circuit Drawing and Editing Program for Use with A Storage-tube Display Terminal

2023-03-30T03:55:57Z

Case Study in Interactive Graphics Programming: A Circuit Drawing and Editing Program for Use with A Storage-tube Display Terminal Brackett, J.; Hammer, M.M.; Thornhill, D. The concepts involved in building and manipulating a data structure through graphical interaction are presented, using the drawing and editing of electrical circuits as a vehicle. The circuit drawings program was designed to operate on an ARDS storage-tube display terminal attached to the M.I.T. Project MAC IBM 7094 Compatible Time-Sharing System.

EPS: An Interactive System for Solving Elliptic Boundary-Value Problems with Facilities for Data Manipulation

2023-03-30T04:17:38Z

EPS: An Interactive System for Solving Elliptic Boundary-Value Problems with Facilities for Data Manipulation Tillman, Coyt C., Jr. This appendix for the author's forthcoming thesis, "On-Line Solution of Elliptic Boundary-Value Problems," is a user's guide for EPS. EPS solves two-dimensional boundary-value problems for elliptic systems of second-order partial differential equations. It also has general-purpose capabilities which permit the on-line definition and execution of arbitrary numerical procedures.

Interactive Computer-mediated Animation

2023-03-30T03:54:11Z

Interactive Computer-mediated Animation Baeker, Ronald M. The use of interactive computer graphics in the construction of animated visual displays is investigated. The dissertation presents a process called interactive computer-mediated animation, in which dynamic displays are constructed by utilizing direct console commands, algorithms, free-hand sketches, and real-time actions. The resulting "movie" can then be immediately viewed and altered.

A Formal System for Defining the Syntax and Semantics of Computer Languages

2023-03-30T04:06:48Z

A Formal System for Defining the Syntax and Semantics of Computer Languages Ledgard, Henry Francis The thesis of this dissertation is that formal definitions of the syntax and semantics of computer languages are needed. This dissertation investigates two candidates for formally defining computer languages: (1) the formalism of canonical systems for defining the syntax of a computer language and its translation into a target language for defining the semantics of a computer language.

Computer Recognition of Three-Dimensional Objects in a Visual Scene

2023-03-30T03:36:39Z

Computer Recognition of Three-Dimensional Objects in a Visual Scene Guzman-Arenas, Aldolfo Methods are presented 1) to partition or decompose a visual scene into the bodies forming it; (2) to position these bodies in three-dimensional space, by combining two scenes that make a stereoscopic pair; 3) to find the regions or zones of a visual scene that belong to its background, (4) to carry out the isolation of objects in (1) when the input has inaccuracies.

A Simulator of Multiple Interactive Users to Drive a Time-shared Computer System

2023-03-30T04:08:10Z

A Simulator of Multiple Interactive Users to Drive a Time-shared Computer System Greenbaum, Howard Jacques In the construction and maintenance of a time-shared computer system the need arises for a tool which can provide a controlled, repeatable environment for the purpose of making performance measurements. This thesis describes the use of a small second computer to simulate the actions of multiple interactive users over individual communication lines. Each simulated user exhibits responses similar to those of a "normal" interactive user.

Lambda Calculus Models of Programming Languages

2023-03-30T04:25:10Z

Lambda Calculus Models of Programming Languages Morris, James H. Two aspects of programming languages, recursive definitions and type declarations are analyzed in detail. Church's -calculus is used as a model of a programming language for purposes of the analysis. The main result on recursion is an analogue to Kleene's first recursion theorem: If A= FA for any A-expressions A and F, then A is an extension of YF in the sense that if E[YE], any expressions containing YF, has a normal form then E[F] =E {A]. Y is Curry's paradoxical combinator. The result is shown to be invariant for many different versions of Y.

An Integrated Hardware-software Systems for Computer Graphics in Time-sharing

2023-03-30T03:06:03Z

An Integrated Hardware-software Systems for Computer Graphics in Time-sharing Thornhill, D.E.; Stotz, R.H.; Ross, D.T.; Ward, J.E. This report describes the ESL Display Console and its associated user-oriented software systems developed by the M.I.T. Computer-Aided Design Project with Project MAC. Console facilities include hardware projection of three-dimensional line drawings, automatic light pen tracking, and a flexible set of knob, switch, and push-button inputs. The console is attached to the Project MAC IBM 7094 Compatible Time-Sharing System either directly or through a PDP-7 Computer.

Implementing Multi-process Primitives in a Multiplexed Computer System

2023-03-30T03:27:23Z

Implementing Multi-process Primitives in a Multiplexed Computer System Rappaport, Robert Lee In any computer system primitive functions are needed to control the actions of processes in the system. This thesis discusses a set of six such process control primitives which are sufficient to solve many of the problems involved in parallel processing as well as in the efficient multiplexing of system resources among the many processes in a system.

The Graph Display as an Aid in the Monitoring of a Time-shared Computer System

2023-03-30T04:23:52Z

The Graph Display as an Aid in the Monitoring of a Time-shared Computer System Grochow, Jerrold Marvin The problem of dynamic observation of the state of a time-shared computer system is investigated. The Graphical Display Monitoring System was developed as a medium for this experimental work. It is an integrated system for creating graphic displays, dynamically retrieving data from Multics Time-Sharing Systems supervisor data bases, and on-line viewing of this data viewing of this data via the graphics displays.

Absenetee Computations in a Multiple-access Computer System

2023-03-30T03:06:18Z

Absenetee Computations in a Multiple-access Computer System Deital, H.M. in multiple-access computer systems, emphasis is placed upon serving several interactive users simultaneously. However, many computations do not require user interaction, and user may therefore want to run these computations 'absentee' (or, user not present). A mechanism is presented which provides for the handling of absentee computations in a multiple-access computer system.

CARPS, A Program Which Solves Calculus Word Problems

2023-03-30T04:23:57Z

CARPS, A Program Which Solves Calculus Word Problems Charniak, Eugene A program was written to solve calculus word problems. The program CARPS (Calculus Rate Problem Solver), is restricted to rate problems. The overall plan of the program is similar to Bobrow's STUDENT, the primary difference being the introduction of "structures" as the internal model in CARPS. Structures are stored internally as trees. Each structures is designed to hold the information gathered about one object.

Resource Allocation in Multiprocess Computer Systems

2023-03-30T03:39:16Z

Resource Allocation in Multiprocess Computer Systems Denning, Peter James The dynamic allocation for limited processor and main memory resources among members of a user community is investigated as a supply-and-demand problem. The work is divided into four phases. First phase is the construction of the working set model for program behavior. This model is based on locality, the concept that, during any interval of execution, a program favors a subset of its information; a computation's working set is a dynamic measure of this set of favored information. A working set storage management policy is one that allocates processors to a computation if and only if there is enough uncommitted space in main memory to contain its working set.

Incremental Simulation on a Time-shared Computer

2023-03-30T03:02:34Z

Incremental Simulation on a Time-shared Computer Jones, Malcolm Murray This thesis describes a system which allows simulation models to be built and tested incrementally. It is called OPS-4 and is specifically designed to operate in the environment of the Multics system. It represents a major expansion and improvement of the OPS-3 system implemented in CTSS and also includes many features adapted from other current simulation systems.

Symbolic Integration

2023-03-30T03:22:52Z

Symbolic Integration Moses, Joel SIN and SOLDIER are heuristic programs written in LISP which solve symbolic integration problems. SIN (Symbolic INtegrator) solves indefinite integration problems at the difficulty approaching those in the larger integral tables. SIN contains several more methods than are used in the previous symbolic integration program SAINT, and solves most of the problems attempted by SAINT in less than one second. SOLDIER (SOLution of Ordinary Differential Equations Routine) solves first order, first degree ordinary differential equations at the level of a good college sophomore and at an average of about five seconds per problem attempted.

A Canonic Translator

2023-04-07T17:11:52Z

A Canonic Translator Alsop, Joseph Wright An algorithm to recognize and translate sets of character strings specified by canonic system is presented. The ability of canonic systems to define the context sensitive features of strings and to specify their translation allows the algorithm to recognize and translate real computer languages. It is also applicable in other languages systems.

On the Simulation of Dynamic Systems with Lumped Parameters and Time Delays

2023-03-30T03:31:32Z

On the Simulation of Dynamic Systems with Lumped Parameters and Time Delays Leal-Cantu, Nestor

A System for Computer-aided Diagnosis

2023-03-30T03:41:37Z

A System for Computer-aided Diagnosis Gorry, Gregory Anthony This thesis describes a model diagnostic problem and a computer program designed to deal with this problem. The model diagnostic problem is an abstract problem. A major contention of this thesis, however, is that this problem subsumes the principal feature of a number of ostensibly different real diagnostic problems including certain problems of medical diagnosis and the diagnosis of machine failures. A second major contention of this thesis is that strategies for the solution of the model diagnostic problem can be formulated in terms sufficiently explicit to permit their incorporation in a computer program.

Program Analysis by Digital Computer

2023-03-30T03:10:34Z

Program Analysis by Digital Computer Wilde, Daniel Underwood A comparison of the properties of non-modifying and self-modifying programs leads to the definition of independent and dependent instructions. Because non-modifying programs contain only independent instructions, such programs can be analyzed by a straight forward, two -step analysis procedure. First, the program control flow is detected; second, that control flow is used to determine the program data flow or data processing. However, self-modifying programs can also contain dependent instructions, and the program control flows and data flows exhibit cyclic interaction.

Design and Implementation of a Table-Driven Compiler System

2023-03-30T04:24:37Z

Design and Implementation of a Table-Driven Compiler System Liu, Chung L.; Change, Gabriel D.; Marks, Richard E. Our goal is to provide users of the table-driven compiler system with an environment within which they can freely design and produce their compilers. The primary design criterion is generality so that the users can define a large class of input languages oriented toward any kind of problem-solving purposes, and can also define a large class of object programs to be executed on different computer systems. Therefore, in our system we do not limit the users to specific ways of doing syntactic analysis, or doing storage allocation, or producing binary programs of a specific format for a particular computer system. What we provide are mechanisms that are general enough for whichever way a user desires to build his compiler.

Surfaces for Computer-aided Design of Space Forms

2023-03-30T04:07:59Z

Surfaces for Computer-aided Design of Space Forms Coons, Steven A. The design of airplanes, ships, automobiles, and so-called ""sculptured parts"" involves the design, delineation, and mathematical description of bounding surfaces. A method is described which makes possible the description of free-form doubly curved surfaces of a very general kind. An extension of these ideas to hyper-surfaces in higher dimensional spaces is also indicated.

On-line Analysis for Social Scientists

2023-03-30T03:47:05Z

On-line Analysis for Social Scientists Miller, James R. A library of computer routines has been compiled to facilitate the analysis of social science research data. Many of these routines are designed to test statistical hypotheses. All routines are operated on-line and permit conversational interaction between the user and a time-shared computer. Input data are typed directly into the computer through a teletype console. Explicit typing directions and error diagnostics, where appropriate, are printed out by each routine to guide the input process. Analyses are executed immediately, and computed results are printed out in typical publication language.

Syntax-based Analytic Reading of Musical Scores

2023-03-30T03:31:47Z

Syntax-based Analytic Reading of Musical Scores Forte, Allen As part of a larger research project in musical structure, a program has been written which ""reads"" scores encoded in an input language isomorphic to music notation. The program is believed to be the first of its kind. From a small number of parsing rules the program derives complex configurations, each of which is associated with a set of reference points in a numerical representation of a time-comtinuum. The logical structure of the program is such that all and only the defined classes of events are represented in the output.

A Low-cost Output Terminal for Time-shared Computers

2023-03-30T03:13:29Z

A Low-cost Output Terminal for Time-shared Computers Rosenburg, Ronald C.; Kennedy, Daniel W.; Humphrey, Roger A. This report describes a low-cost remote terminal to provide switch-form output from a time-shared digital computer. The terminal consists of a modified model 35 KSR teletype and a local memory unit. The unit is independent of any particular computer, and is easy to test and maintain. The states of the memory control and memory words are observable directly by indicator lights.

Some Aspects of Pattrn Recognition by Computer

2023-03-30T03:01:25Z

Some Aspects of Pattrn Recognition by Computer Guzman-Arenas, Adolfo A computer may gather a lot of information from its environment in an optical or graphical manner. A scene, as seen for instance from a TV camera or a picture, can be transformed into a symbolic description of points and lines or surfaces. This thesis describes several programs, written in the language CONVERT, for the analysis of such descriptions in order to recognize, differentiate and identify desired objects or classes of objects in the scene. Examples are given in each case.

An On-line System for Algebraic Manipulation

2023-03-30T04:07:43Z

An On-line System for Algebraic Manipulation Fenichel, Robert R. This thesis describes an approach to the problem of programming a computer for algebraic manipulation. The motivating threads of the work are first picked up in Chapter I. To test the descriptive intuitions urged normatively in Chapter I, an experimental system was actually implemented. This system is described in Chapter II and in the Appendices.

Computer Design for Asynchronously Reproducible Multiprocessing

2023-03-30T03:58:15Z

Computer Design for Asynchronously Reproducible Multiprocessing Van Horn, Earl C. A concept is presented for designing either a computing system, or a programming language system, so that the following problem is avoided: during a multiprocess computation in which several processes communicate, and in which the relative timing of the processes is arbitrary, the output produced by the computation might not be a function of only the initial computation state, i.e., of only the inputs and initial program of the computation.

ADEPT: A Heuristic Program for Proving Theorems of Group Theory

2023-03-30T03:02:21Z

ADEPT: A Heuristic Program for Proving Theorems of Group Theory Norton, Lewis Mark A computer program, named ADEPT (A Distinctly Empirical Prover of Theorems), has been written which proves theorems taken from the abstract theory of groups. Its organization is basically heuristic, incorporating many of the techniques of the human mathematician in a "natural" way. This program has proved almost 100 theorems, as well as serving as a vehicle for testing and evaluating special-purpose heuristics.

Pilot: A Step Towards Man-Computer Symbiosis

2023-03-30T03:29:29Z

Pilot: A Step Towards Man-Computer Symbiosis Teitelman, Warren PILOT is a programming system constructed in LISP. It is designed to facilitate the development of programs by easing the familiar sequence: write some code, run the program, make some changes, write some more code, run the program again, etc. As a program becomes more complex, making theses changes becomes harder and harder because the implications of changes are harder to anticipate.

Models and Data Structures for Digital Logic Simulation

2023-03-30T03:39:30Z

Models and Data Structures for Digital Logic Simulation Smith, Donald Leigh A digital logic simulation system is proposed for design verification. Logic to be simulated is specified with a high level register transfer design language, and the simulation system operates on-line on a large time-shared computer. The problem of selecting adequate circuit and signal models for this purpose is considered. models are proposed with sufficient timing detail to allow the simulation system to detect timing errors which currently are found by manual checking or prototype.

Traffic Control in a Multiplexed Computer System

2023-03-30T04:14:55Z

Traffic Control in a Multiplexed Computer System Saltzer, Jerome H. This thesis describes a scheme for processor multiplexing in a multiple user, multiple processor computer system. The scheme is based upon a distributed supervisor which may be different for different users. The processor multiplexing method provides smooth inter-process communication, treatment of input/output control as a special case of inter-process communication, and provision for a user to specify parallel processing or simultaneous input/output without interrupt logic.

Search Procedures Based on Measures of Relatedness Between Documents

2023-03-30T03:27:36Z

Search Procedures Based on Measures of Relatedness Between Documents Ivie, Evan Leon In this thesis a new type of information retrieval system is suggested which utilizes data of the type generated by the users of the system instead of data generated by indexers. The theoretical model on which the system is based consists of three basic elements. The first element is measure of the relatedness between document-pairs. It is derived from information theory.

Input/Output in Time-shared, Segmented, Multiprocessor Systems

2023-03-30T04:07:35Z

Input/Output in Time-shared, Segmented, Multiprocessor Systems Smith, Arthur Anshel After introducing and defining the concepts of time-sharing, segmentation, and multiprocessing, two classes of systems incorporating these are introduced. Both classes use associative memories, as 'look behind' devices to speed the operation of addressing the segment memory, with the distinction between classes being the location of the associative memory.

OCAS - On-line Cryptanalytic Aid System

2023-03-30T04:08:29Z

OCAS - On-line Cryptanalytic Aid System Edwards, Daniel James Deficiencies of various programming languages for dealing with quantities frequently encountered in cryptanalysis of simple cipher systems will be discussed. A programming system is proposed which will permit a cryptanalyst to write and debug programs to aid in he solution of cryptograms or cryptographic systems. The basic elements of the proposed programming system are discussed in detail. They include: 1) a programming language to handle both algebraic quantities and character strings, 2) a display generator to permit quick specification of a display frame containing both alphanumeric strings and numerical data for an on-line CRT display device, and 2) an on-line program to control operation of the system and in debugging programs written in the proposed language.

Design of a Low-cost Character Generator for Remote Computer Displays

2023-03-30T03:54:42Z

Design of a Low-cost Character Generator for Remote Computer Displays Cheek, Thomas Burrell A requirement exists for a low-cost remote display terminal with alphanumeric and line-drawing capabilities for use with time-shared computer systems. This thesis, conducted as part of the overall remote display design project, was undertaken to investigate novel approaches to character generation, with the goal of drastically reducing present-day costs for such devices. A survey of existing devices and character generation techniques was carried out, and a design approach was chosen which takes advantage of mass-fabrication techniques. This includes using a five-by-seven dot matrix raster and a resistor array "read-only" character memory for the 96 printable symbols of the Revised Proposed ASCII Code. Circuits designed, included a dot matrix generator and a register array memory with selection logic sense amplifiers, and a shift register output buffer. An experimental character generator with an eight-word memory was built, largely using integrated circuits and was found to work as desired. It is concluded that the design approach will yield a character generator that is of low enough cost to find wide use in remote computer terminals.

Investigation of an Analog Technique to Decrease Pentracking Time in Computer Display

2023-03-30T04:06:55Z

Investigation of an Analog Technique to Decrease Pentracking Time in Computer Display Stratton, William David Many modern digital computer systems contain cathode-ray tube display equipment to facilitate man-machine communications. Through the use of a display and a light-sensitive pen, graphical material can be directly inserted into the computer by using the pen to control the position of the electron beam at the face of the CRT-a process called pen tracking. Beam position is continually sampled by the computer, permitting continuous display of the material being sketched. In present digital pen-tracking techniques, a tracking pattern (usually a cross) with a substantial number of points is generated on the face of the CRT and the binary response of the pen to the individual points of the pattern is employed to calculate pen position. The large number of pattern points, and the phosphor decay time associated with each, yield a typical tracking cycle of 500 to 1000 microseconds. Since the cycle must be repeated about 100 times per second, 5 to 10 percent of display time is consumed. To reduce the time required by the tracking operation, an analog technique employing a four-point tracking pattern is proposed in this study, in which the amplitude response of the pen to corresponding pairs of points is used to determine the position of the pen relative to the center of the pattern. To study the method, one channel of the proposed two-channel analog tracking system was designed, constructed, and coupled to the horizontal channel of a high-speed computer display console. To avoid the phosphor-decay limitation, an experimental "Beam" pen capable of detecting the electron beam rather than the phosphor luminescence is employed. The system included a pattern generator, sample-and-hold gates, difference amplifier, envelope detector and noise filter, and a threshold-logic analog-to-digital converter. The time required to generate the tracking pattern and develop the binary equivalent of the horizontal distance separating pen and pattern center is only 25 microseconds. Tracking is generally satisfactory, but some anomalies were noted, apparently due to the characteristics of the experimental pen being used. It is concluded that the analog technique is feasible for improving the speed of pen tracking, but recommended that further studies be made of the limitations inherent in the method.

MAP: A System for On-line Mathematical Analysis

2023-03-30T04:07:12Z

MAP: A System for On-line Mathematical Analysis Kaplow, Roy; Strong, Stephen; Brackett, John This manual describes a computer suitable for use on the time-sharing facility at the M.I.T. Computation Center or at Project MAC. Designated for direct computer access through a remote console, the system replaces the normal procedures of programming with a question and answer interchange between the user (hereinafter called U) and the computer (hereinafter called C). The system is intended for the solution of mathematical problems. It should be usable by a person with no knowledge of computers or programming and little knowledge of numerical analysis. Within its range of capabilities, it should be as efficient as are the normal means of computer access for the more sophisticated user. The system establishes a "conversation" between U and C with an electric typewriter as the means of communication. U can give information to C and can ask it certain questions. C can answer those questions if it is given enough information. C can also ask questions and can therefore request any missing information. In addition, C can explain procedures to U in order to help the latter transmit the required information in a proper form. U, therefore, only needs to know a few basic rules, such as how to phrase his questions and how to name and tabulate his data.

Programming Semantics for Multiprogrammed Computations

2023-03-30T03:58:54Z

Programming Semantics for Multiprogrammed Computations Dennis, Jack B.; Van Jhorn, Earl C. The semantics are defined for a number of meta-instructions which perform operations essential to the writing of programs in multiprogrammed computer systems. These meta-instructions relate to parallel procession, protection of separate computations, program debugging, and the sharing among users of memory segments and other computing objects, the names of which are hierarchically structured. The language sophistication contemplated is midway between an assembly language and an advanced algebraic language.

The Priority Problem

2023-03-30T04:15:03Z

The Priority Problem Greenberger, Martin Priority decisions arise whenever limited facilities must be apportioned among competitive demands for service. Broadly viewed, even the familiar first-come-first served discipline is a priority rule. It favors the longest-waiting user, and guards against excessive delays. Other priority rules, such as shortest-job-next, are keyed instead to considerations of operating efficiency. Urgency of request is still another common consideration. Since these considerations often conflict, the priority rule serves as mediator. Use of a common cost measure can help effect this mediation, as results from recent job-shop simulations illustrate. A priority operation of contemporary interest is scheduling a time-shared computer among its concurrent users. Service requirements are not known in advance of execution. To keep response times short for small requests, service intervals are partitioned and segments are served separately in round-robin fashion. A mathematical analysis pinpoints the tradeoff between overhead and discrimination implicit in this procedure, and allows alternate strategies to be costed. Extensions of the simple round-robin procedure are suggested, the objectives of time-sharing are reviewed, and implications are drawn for the design of future priority and pricing systems.

Queueing Models for File Memory Operation

2023-03-30T04:04:47Z

Queueing Models for File Memory Operation Denning, Peter James A model for the auxiliary memory function of a segmented, multiprocessor, time-shared computer system is set up. A drum system in particular is discussed, although no loss of generality is implied by limiting the discussion to drums. Particular attention is given to the queue of requests waiting for drum use. It is shown that a shortest access time first queue discipline is the most efficient, with the access time being defined as the time required for the drum to be positioned, and is measured from the finish of service of the last request to the beginning of the data transfer for the present request. A detailed study of the shortest access time queue is made, giving the minimum access time probability distribution, equations for the number in the queue, and equations for the wait in the queue. Simulations were used to verify these equations; the results are discussed. Finally, a general Markov Model for Queues is discussed in an Appendix.

Calculaid: An On-line System for Algebraic Computation and Analysis

2023-03-30T03:46:51Z

Calculaid: An On-line System for Algebraic Computation and Analysis Wantman, Mayer Elihu OPS is an on-line system developed by M. Greenberger et al. at Project MAC. The present work provides a powerful and simple way to perform numerical manipulations and calculations within OPS. The program package is called CALCULAID. A method of executing algebraic assignment statements, of which MAD and FORTRAN assignments are a subset, is provided. When this assignment-statement ability is coupled with other features of the OPS system, such as unconditional transfers, general conditionals, and array and function declarations, most of the ability of a compiler language is provided. Because the programs written in OPS are executed interpretively, OPS-3 programs can be changed and re-run immediately, without being compiled. The other elements of CALCULAID are a program for creating multiple linear regression models, rank-ordering and counting data, and finding roots to polynomial equations in one unknown. The applications of CALCULAID to the analysis of a round-robin scheduling model and to a process-control problem are discussed, and conclusions regarding the suitability of running computational programs in an interpretive mode are drawn.

A Heuristic Approach to Alternate Routing in a Job Shop

2023-03-30T04:16:40Z

A Heuristic Approach to Alternate Routing in a Job Shop Russo, F.J. The research reported here investigates the use of heuristics for selecting from several alternate routes resulting from partially ordered tasks in a job shop order file. The experimental vehicle employed was digital simulation. The concept of the "Alternate string" has been developed to generalize the existence of partially ordered operations. That term is defined as a concatenation of operations that can be performed in any order, with the additional specification that all within the string can be attempted. The presence of alternate strings with two or more member gives rise to the alternate routing problem, whose solution is approached by heuristic methods. Choosing from among several alternate routes constitutes a three level decision problem. At the lowest level, routes can be chosen when the order enters the shop. This is equivalent to fixed routing. At a higher level, alternates can be selected at the time of transition from one work station to another. The third decision level occurs at operation time, when one of the alternate operations is placed on a machine. Heuristics were tested at the latter two levels. There were two prior assertions that this thesis set out to prove. The first was that alternate routing at the highest decision level would produce significant reductions in the mean tardiness of orders completed past their designated due dates, the improvement being both relative to fixed routing and to alternate routing heuristics implemented at lower decision levels. Secondly, the contention was made that the improvement would be as such a magnitude that on-line, real-time systems become economically justifiable as a means of mitigating the attendant control problems caused by non-deterministic paths through the queuing network. The methodology employed here was to conduct two passes of simulated shop runs. The first, with two artificially high levels of alternate incidence, tested the efficiency of five different alternate routing heuristics in reducing mean tardiness. The second pass consisted of runs with the best heuristic developed during the first experimental phase applied to a realistic length and frequency of alternate strings. The results of the experiments strongly support the assertions made at the outset of the thesis. The performance characteristics of the different heuristics are discussed at length. In addition, some implications are drawn of the computational nature of alternate routing and the difficulties encountered in implementing alternate routing heuristics at operation time.

An Analysis of Time-Shared Computer Systems

2023-04-07T16:21:06Z

An Analysis of Time-Shared Computer Systems Scherr, Allan Lee Some of the aspects of the operation of time-shared, interactive computer systems are analyzed. The emphasis is on the reaction of hardware systems to the demands that its users make upon it. Simply shared systems and their users in order to be able to predict the performance of the two operating together. Portions of this problem include the specification and measurement of user characteristics, the development and verification of both simulation and mathematical models for time-shared systems, and the specification and measurement of performance metrics for such systems. The user and some of the performance measurements were made on Project MAC's "Compatible Time-Sharing System" (CTSS). First, simulation models are used to study the effects of changing small details in the operation of CTS-like systems. Then, a continuous-time Markov process model is derived to predict the performance of a broad class of systems. Throughout, the CTSS data are used as a basis for comparison with model predictions. In order to be able to take measurements and to build models, many definitions of commonly used time-shared system terminology are made precise.

Time Sharing on a Multiconsole Computer

2023-03-30T03:48:18Z

Time Sharing on a Multiconsole Computer Samuel, Arthur L. After a brief historical review and a description of the three basic types for time-sharing systems, the general purpose time-sharing system as exemplified by the M.I.T. CTSS system is described in general terms, with particular attention to the way the system looks to the user.

CTSS Technical Notes

2023-03-30T03:30:27Z

CTSS Technical Notes Saltzer, Jerome H. This report is a technical description of the 7094 Compatible Time-Sharing System in use at Project MAC and the M.I.T. Computation Center. It is designed to acquaint a system programmer with the techniques of construction which were used in this particular time-sharing system. Separate chapters discuss the overall supervisor program flow: console message input and output: the scheduling and storage algorithms: and a thumbnail sketch is given of each of the subroutines which make up the supervisor program. This report was prepared with the aid of the compatible time-sharing system and the TYPSET and RUNOFF commands.

Use of CTSS in a Teaching Environment

2023-03-30T03:32:20Z

Use of CTSS in a Teaching Environment Roos, Daniel Computer time-sharing offers many interesting possibilities for use in teaching computer technology. It might be expected that with proper hardware and software, students using time-sharing as a teaching machine could acquire proficiency in the fundamentals of programming more easily than using batch-processing. To test this hypothesis, the M.I.T. Department of Civil Engineering divided a freshman programming class so that half the students used batch-processing methods, and half used the Project MAC time-sharing system to do the same work. This paper describes the experiment and its tentative results.

A New Methodology for Computer Simulation

2023-03-30T04:20:42Z

A New Methodology for Computer Simulation Greenberger, Martin Computer simulation is a cooperative venture between researcher and information processor, but the processor's role customarily begins too late. The researcher can benefit substantially by bringing the computer up into the earlier, creative phases of the simulation process. An on-line computer system that makes this possible is described.

The MAC System: A Progress Report

2023-03-30T03:18:43Z

The MAC System: A Progress Report Fano, Robert M. The notion of machine-aided cognition implies an intimate collaboration between a human user and a computer in a real-time dialogue on the solution of a problem, in which the two parties contribute their best capabilities. In order for this intimate collaboration to be possible, a computer system is needed that can serve simultaneously a large number of people, and that is easily accessible to them, both physically and intellectually. The present MAC System is a first step toward this goal. The purpose of this paper is to present a brief description of the current system, to report on the experience gained from its operation, and to indicate directions along which future developments are like to proceed.

Program Structure in a Multi-access Computer

2023-03-30T04:17:34Z

Program Structure in a Multi-access Computer Dennis, Jack B. A multi-access computer (MAC) system consists of processing units and directly addressable main memory in which procedure information is interpreted as sequences of operations on data, a system of terminal devices through which users may communicate with procedures operating for them, and mass memory where procedures and data may be held when not required for immediate reference. One fundamental attraction of the MAC concept is the increased productivity of "computer catalyzed research" that results from close man-machine interaction. Another attraction is wealth of data and procedures that are accessible to a large user community through the file memory of a MAC system. In this report thoughts are developed which form an adequate model of program structure. These concepts have grown out of many discussions with colleges in Project MAC, and our experience to date in the design and operation of multi-access computer systems.

The OPS-1 Manual

2023-03-30T03:49:52Z

The OPS-1 Manual Greenberger, Martin The recent attainment and continuing development of personally accessible computer facilities have opened another chapter in the use of machines by man. A number of current research efforts, including Project MAC at M.I.T., are designing new conceptual systems to adapt the emerging technology to a wide range of human activity. Activities relating to management are the concern of a trial system at Project MAC called OPS-1. The OPS-1 system and the experiment that launched it are described in this manual. {AD 604-681}

OPL-I An Open Ended Programming System Within CTSS

2023-03-30T03:13:59Z

OPL-I An Open Ended Programming System Within CTSS Weizenbaum, Joseph OPL-1, an incremental programming system presently operating with CTSS, permits the user to augment both his program and his data base during widely separated successive sessions at his terminal. Facilities are provided which make it possible for the user to operate on his already established data base both by means of built-in operators and in terms of operators (functions) which the user has previously defined in the language of the system. Underlying the system is a powerful list processing scheme embedded in FORTRAN (SLIP). The machinery of this fundamental language drives the system and is also largely available to the user. The data base generated by the user is therefore a set of list structures (trees), and most of the operators available to him are list processing operators. Data structures with considerably complex inter-relational properties may therefore be treated quite directly.

Stress: A Problem-oriented Language for Structural Engineering

2023-03-30T03:40:05Z

Stress: A Problem-oriented Language for Structural Engineering Biggs, John M.; Logcher, Robert D. STRESS is a general purpose programming system for the analysis of structures. Compared to most other structural programs it has three distinguishing characteristics: (1) The input language is that of the structural engineer which makes possible direct communication between the engineer and the machine; (2) The system is capable of analyzing a wide variety of structural types and loading conditions thus permitting industrial use on a routine basis; and (3) The design process is expedited by the fact that modifications of the original structure for alternate designs can be easily executed. This last capability is most effective when STRESS is used in the time-sharing mode. These features combine to provide a system which not only reduces the effort required for structural analysis but, more significantly, enhances the designer's ability to evolve an efficient structure.

CARPS, A Program Which Solves Calculus Word Problems

2023-03-30T03:54:02Z

CARPS, A Program Which Solves Calculus Word Problems Charniak, Eugene

Verbal and Graphical Language for the AED System: A Progress Report

2023-03-30T04:03:18Z

Verbal and Graphical Language for the AED System: A Progress Report Ross, Douglas T.; Feldman, Clarence G. For Computer-Aided Design, use of time-sharing a single language which can take either verbal or graphical form is required. This paper describes how a single language processing technique, which is in turn a special application of more general concepts concerning the step-by-step growth and processing of large structures of interrelated elements, can efficiently process both language forms in the same manner. Illustrations of the concepts involved are also drawn from the methods used in the AED-O Compiler, an efficient ALGOL-60-based compiler used in Computer-Aided Design work, which is available as a public command in the Project MAC CTSS.

System Requirements for Multiple -Access, Time-shared Computers

2023-03-30T03:57:28Z

System Requirements for Multiple -Access, Time-shared Computers Corbató, Fernando J. It is now clear that it is possible to create a general-purpose time-shared multiple access system on most contemporary computers. However, it is equally clear that none of the existent computers are well designed for multiple access systems. At present, good service to a few dozen simultaneous users is considered state-of-the-art. Discussions include: clocks, memory protection and supervisor mode, program relocation and common subroutines which expose the reader to the difficulties encountered with contemporary machines when multiple user multiple-processor systems are considered.

SIR: A Computer Program for Semantic Information Retrieval

2023-03-30T03:33:51Z

SIR: A Computer Program for Semantic Information Retrieval Raphael, Bertram SIR is a computer system, programmed in the LISP language, which accepts information and answers questions expressed in a restricted form of English. This system demonstrates what can reasonably be called an ability to "understand" semantic information. SIR's semantic and deductive ability is based on the construction of an internal model, which uses word associations and property lists, for the relational information normally conveyed in conversational statements. A format-matching procedure extracts semantic content from English sentences. If an input sentence is declarative, the system adds appropriate information to the model. If an input sentence is a question, the system searches the model until it either finds the answer or determines why it cannot find the answer. In all cases SIR reports its conclusions. The system has some capacity to recognize exceptions to general rules, resolve certain semantic ambiguities, and modify its model structure in order to save computer memory space. Judging from its conversational ability, SIR is more "intelligent" than any existing question-answering system. The author describes how this ability was developed and how the basic features of SIR compare with those of other systems. The working system, SIR , is a first step toward intelligent machine communication. The author proposes a next step by describing how to construct a more general system which is less complex and yet more powerful than SIR . This proposed system contains a generalized version of the SIR model, a formal logical system called SIR1 , and a computer program for testing the truth of SIR1 statements with respect to the generalized model by using partial proof procedures in the predicate calculus. The thesis also describes the formal properties of SIR1 and how they relate to the logical structure of SIR .

Natural Language Input for a Computer Problem Solving System

2023-03-30T03:11:51Z

Natural Language Input for a Computer Problem Solving System Bobrow, Daniel .G The STUDENT problem solving system, programmed in LISP, accepts as input a comfortable but restricted subset of English which can express a wide variety of algebra story problems. STUDENT finds the solution to a large class of these problems. STUDENT can utilize a store of global information not specific to any one problem, and may make assumptions about the interpretation of ambiguities in the wording of the problem being solved. If it uses such information, or makes any assumptions, STUDENT communicates this fact to the user. The thesis includes a summary of other English language question-answering systems. All these systems, and STUDENT are evaluated according to four standard criteria. The linguistic analysis in STUDENT is a first approximation to the analytic portion of a semantic theory of discourse outlined in the thesis. STUDENT finds the set of kernel sentences which are the base of the input discourse, and transforms this sequence of kernel sentences into a set of simultaneous equations which form the semantic base of the Student system. STUDENT then tries to solve this set of equations for the values of requested unknowns. If it is successful it gives the answers in English. If not, STUDENT asks the user for more information, and indicates the nature of the desired information. The STUDENT system is a first step toward natural language communication with computers. Further work on the semantic theory proposed should result in much more sophisticated systems.