In its first five years, the Architectural Association's Diploma unit II developed the theoretical framework of an alternative generative process, using computer models to compress evolutionary space and time. This led to a prototype that could be demonstrated interactively and the launch on the Internet of an experimental evolutionary environment which attracted global participation, established a dematerialised model. The new phase of the programme has begun to externalise this conceptual model into constructed form, focusing on urban-scale evolution and other historical and natural examples of co-operative and ecologically i integrated development. The approach has been to consider metabolic processes as a way of understanding both the formal development of urban symbiosis and the specific problem of materialization. The city planning department of Groningen commissioned a small working prototype demonstration of a predictive urban computer model. The unit produced an evolving model which explains the transition from the past to the present, and projects future trajectories a “what if” model for generating, exploring and evaluating alternatives. The model mediates in scale, space and time:, in scale between the urban context and the fine grain of the housing typologies, in space between the existing fabric of Groningen and specific dwelling units, in time between the lifestyle within the medieval core and the desires of the citizens of tile next century