||Design is a cooperative activity at several levels. At one level, clients, architects, financiers, and construction engineers and contractors, all play important roles in creating the design for the building. At another level, the design team may contain architects, interior and landscape designers, lighting experts, heating, ventilation, and air-conditioning experts, etc. At a third level, individual architects cooperate with computer-based design tools in creating portions of a complex design. This paper describes an ongoing project called ArchiDATA, in which we are developing a computational Case-Based Design Aid (CBDA) for architectural design. This project, which is collaboration between cognitive scientists and architectural researchers, builds on an artificial intelligence paradigm called case-based reasoning and work in post-occupancy evaluation and other case study research in architecture.