Descriptive change in architecture: identities in shape grammars and multiplicity in design datasets

This paper argues that changes in descriptions of architectural objects or elements have advanced architecture historically. Description changes are possible when the objects are amenable to a multiplicity of interpretation. We present an original classification of examples to demonstrate descriptive changes ranging from the formation of the Doric order to Romanesque, Gothic, Modern, Postmodern and contemporary architecture. Description changes are represented as rule-based computational processes guided by identity rules, a class of shape rules defined in shape grammars. We ground the abstract computational nature of identity rules on real-world architectural contexts to analyse description changes that have stimulated generative processes—from forming the ancient triglyph to crafting a Gothic pinnacle or spatially and structurally organizing Terragni’s Danteum. The diversity of the examples demonstrates the relevance of descriptive change to all aspects of architectural design, from purely structural to purely ornamental, and flags the importance of multiplicity within design datasets.