Show simple item record

dc.contributor.advisorBrian C. Williams.en_US
dc.contributor.authorElliott, Paul Harrison, 1979-en_US
dc.contributor.otherMassachusetts Institute of Technology. Dept. of Aeronautics and Astronautics.en_US
dc.date.accessioned2005-06-02T18:34:09Z
dc.date.available2005-06-02T18:34:09Z
dc.date.copyright2004en_US
dc.date.issued2004en_US
dc.identifier.urihttp://hdl.handle.net/1721.1/17766
dc.descriptionThesis (S.M.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2004.en_US
dc.descriptionIncludes bibliographical references (p. 109-111).en_US
dc.description.abstractPerforming real-time reasoning on models of physical systems is essential in many situations, especially when human intervention is impossible. Since many deductive reasoning tasks take memory or time that is exponential in the number of variables that appear in the model, efforts need to be made to reduce the size of the models used online. The model can be reduced without sacrificing reasoning ability by targeting the model for a specific task, such as diagnosis or reconfiguration. A model may be reduced through model compilation, an offline process where relations and variables that have no bearing on the particular task are removed. This thesis introduces a novel approach to model compilation, through the generation of projected prime implicates and projected prime implicants. Prime implicates and prime implicants compactly represent the consequences of a logical theory. Projection eliminates model variables and their associated prime implicates or implicants that do not contribute to the particular task. This elimination process reduces the size and number of variables appearing in the model and therefore the complexity of the real-time reasoning problem. This thesis presents a minimal conflict generator that efficiently generates projected prime implicates and projected prime implicants. The projected minimal conflict generator uses a generate-and-test approach, in which the candidate generator finds potential minimal conflicts that are then accepted or rejected by the candidate tester. The candidate generator uses systematic search in combination with an iterative deepening algorithm, in order to reduce the space required by the algorithm to a space that is linear in the number of variables rather than exponential.en_US
dc.description.abstract(cont.) In order to make the algorithm more time efficient, the candidate generator prunes the search space using previously found implicants, as well as minimal conflicts, which identify the sub-spaces that contain no new minimal conflicts. The candidate tester identifies implicants of the model by testing for validity. The tester uses a clause-directed approach along with finite-domain variables to efficiently test for validity. Combined, these techniques allow the tester to test for validity without assigning a value to every variable. The conflict generator was evaluated on randomly generated models; problems in which models with 20 variables, 5 domain elements each, were projected onto 5 variables. All projected prime implicates were generated from models with 20 clauses within 2 seconds, and from models with 80 clauses within 13 seconds.en_US
dc.description.statementofresponsibilityby Paul Harrison Elliott.en_US
dc.format.extent111 p.en_US
dc.format.extent4976969 bytes
dc.format.extent4988252 bytes
dc.format.mimetypeapplication/pdf
dc.format.mimetypeapplication/pdf
dc.language.isoengen_US
dc.publisherMassachusetts Institute of Technologyen_US
dc.rightsM.I.T. theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission. See provided URL for inquiries about permission.en_US
dc.rights.urihttp://dspace.mit.edu/handle/1721.1/7582
dc.subjectAeronautics and Astronautics.en_US
dc.titleAn efficient projected minimal conflict generator for projected prime implicate and implicant generationen_US
dc.typeThesisen_US
dc.description.degreeS.M.en_US
dc.contributor.departmentMassachusetts Institute of Technology. Dept. of Aeronautics and Astronautics.en_US
dc.contributor.departmentMassachusetts Institute of Technology. Department of Aeronautics and Astronautics
dc.identifier.oclc56526173en_US


Files in this item

Thumbnail

This item appears in the following Collection(s)

Show simple item record