Generative Representations Of The Self-organizing Urban Form

Urban fabric is not shaped by a few works taken to be architecture,but rather by a large number of ordinary buildings.It lies in the center of urban morphology that studies the ordinary built form in the processes of formation and transformation.It is far more complex than that fabricated by urban designers and impossible to be represented analytically.Differing from a string-rewriting system,shape grammars supporting emergence by shape calculation provide a methodological approach to unveiling the forming process at the scale of urban fabric.Firstly proposed in 1971,shape grammar advanced quickly and aroused considerable interest in almost all fields of design through the 1980 s and 1990 s.However,its development has slowed down over the past 20 years and seen few methodological breakthroughs in the application to build environments.In order to update the underpinnings of shape grammar to build forms,we reinterpreted shape and shape grammar formalism by definitions and diagrams in the first part,and then formulated two urban grammars based on Chomsky hierarchy in the second part.In part one,the thesis starts from a comparison of the two classic definitions: the four-tuple form from the formal language and the subshape rewriting form.Next,the thesis compares among the means to represent shapes by maximal elements,by graphs,and by visual.Meanwhile,it proposes several ultra simple,Knight-style grammars to illustrate their merits in shape emergence and limits in subshape detection.By diagramming,the thesis reinterprets the three fundamental features of shape grammar—emergence through shape calculation,ambiguity in shape representation and arbitrariness in rule application.While elucidating the shape grammar foundations,we found that the examples shown in Stiny and Gips’ seminal paper(1971)were fractal structures,having not precisely demonstrated the essence of shape grammar.In part two,this thesis has generalized and formalized a context-free grammar and a context-sensitive grammar to describe the self-organizing fabric in which spatial elements are interlocked.We have shown that how generic,bottom-up grammars reproduce the pattern formation,and how rules,rule parameters,and rule conditions represent a piece of urban fabric.Intended for a more general and rigorous grammar,each of the two grammars contains a grammar definition,unambiguous shape representation(s),both symbolic and graphical rule expressions,and a specified manner of rule application.The context-free grammar consists of two subshape driven rules and provides two means to terminate the procedure,with which one can generate a streetlike network or a fabric-like patchwork,respectively.To simulate a piecemeal buildprocess with street segments and plots,we proposed a marker-driven,context-sensitive grammar containing three rule sets to initialize and extend(or terminate)the growth as well as to deal with street intersections.In this grammar,we provided methods for geometric abstraction,included definitions of shapes’ relations,and offered strategies for objects’ numbering and traversal.Compared with previous non-orthogonal,bottomup urban grammar(s),this grammar is more rigorous and contains a fewer number of rules.This thesis attempted to stimulate a revival of interest in shape grammar formalism and in particular,methodological progress in urban morphology and urban design.It has proposed a series of quantitative approaches to structure-preserving algorithms for self-organizing human settlements.This study will contribute to formal methods in representing and designing complex urban forms.