Early Islamic religious architecture in North Africa displays a marked change from earlier Classical and Christian buildings in their general neglect of exteriors in favour of interior (i.e., courtyard) façades. This feature may be due partly to the nature of Islamic worship, as it was common to virtually all early mosques, yet builders in the central and eastern lands of Islam soon began to adopt such exteriorizing features as domes, towers, and colourful decoration. Maghribi builders, however, maintained their preference for modest exteriors for many centuries, mostly focusing decoration on interior façades and spaces, and differentiating it from much Islamic architecture elsewhere.

This paper describes research carried out to develop a parametric urban shape grammar for the Zaouiat Lakhdar quarter of the Medina of Marrakech in Morocco. The goal is to create the basis for a system that could capture some features of the existing urban fabric and apply them in contemporary urban planning and architectural design. The methodology used is described, from the initial historical analysis and fieldwork to the identification of three subgrammars necessary to encode the complexity of the urban preexistences: the urban grammar, the negotiation grammar, and the housing grammar. Top-down and bottom-up approaches to grammar design are analyzed and compared. The bottom-up urban grammar developed is then described, and a hand derivation of the existing urban fabric is proposed. Visual, symbolic, and tagged computer implementations of shape grammars are briefly discussed and a novel design generated by the tagged interpreter is presented.