Ambiguity in the definition of built form

A detailed critical analysis of the definitions of built form as used in urban morphology is reported. The overarching aim of the analysis was to establish a common reference point for examination of the different aspects of urban form in a given case and comparative study of cases from different times and places. Seminal works are examined in detail, in particular those of M. R. G. Conzen, Gianfranco Caniggia and Gian Luigi Maffei. The starting point is the common conception of a hierarchical relationship between buildings, plots and streets and the overlapping of aspects and elements. Different types of ambiguity inherent in the generic structure of built form are identified. Incorporation of these into a rigorous conception of the hierarchy that allows for the richness of overlapping sets reconciles earlier conceptions and accommodates a wide range of specific forms.