SGML : a meta-language for shape grammar

Abstract

A shape grammar develops a drawing through a series of transformations by repeatedly applying if-then rules. Although the rules can be designed, in principle, to construct any type of drawing, the drawings they construct may not necessarily develop in the manner intended by the designer of the grammar. In this thesis, I introduce a shape grammar meta-language that adds power to grammars based on the shape grammar language. Using the shape grammar meta-language, the author of a grammar can: (1) explicitly determine the sequence in which a set of rules is applied; (2) restrict rule application through a filtering process; and (3) use context to guide the rule matching process, all of which provide a guided design experience for the user of the grammar. Three example grammars demonstrate the effectiveness of the meta-language. The first example is the Bilateral Grid grammar which demonstrates how the meta-language facilitates the development of grammars that offer users multiple design choices. The second grammar is the Hexagon Path grammar which demonstrates how the metalanguage is useful in contexts other than architectural design. The third and most ambitious example is the Durand grammar which embodies the floor plan design process described in Précis of the Lectures of Architecture, written by JNL Durand, an eighteenth century architectural educator. Durand's floor plan design process develops a plan through a series of transformations from grid to axis to parti to wall. The corresponding Durand grammar, which consists of 74 rules and 15 macros organized into eight stages, captures Durand's ideas and fills in gaps in Durand's description of his process. A key contribution of this thesis is the seven descriptors that constitute the meta-language. The descriptors are used in grammar rules: (1) to organize a set of rules for the user to choose from; (2) to group together a series of rules; (3) to filter information in a drawing; (4) to constrain where a rule can apply; and (5) to control how a rule is applied. The end result is a language that allows the author to create grammars that guide users by carefully controlling the design process in the manner intended by the author.