Designing as reflective conversation with the materials of a design situation

The paper considers what it means to capture design knowledge by embodying it in procedures that are expressible in a computer program, distinguishing several possible purposes for such an exercise. Following the lead of David Marr's computational approach to vision, emphasis is placed on ‘phenomenological equivalence’ — that is, first defining the functions of designing, and then specifying how people design. The paper goes on to describe design phenomena that a computational strategy of this kind would have to reproduce. All of them are integral to a view of designing as reflective conversation with the materials of a design situation, and depend on the idea of distinctive design worlds constructed by the designer. These phenomena include: the designer's seeing-moving-seeing, the construction of figures from marks on a page, the appreciation of design qualities, the evolution of design intentions in the course of the design process, the recognition of unintended consequences of move experiments, the storage and deployment of prototypes, which must be placed in transaction with the design situation, and communication across divergent design worlds. Considered as performance criteria for a phenomenologically equivalent computational designer, these phenomena are formidable and threatening. Considered as performance criteria for the construction of a computer-based design assistant, however, they may be highly evocative.