Design Knowledge Capture and Alternatives Generation Using Possibility Tables in Canard1

During the evolution of a design concept, designers must integrate diverse sources and kinds of information about requirements, constraints, and tradeoffs. In doing so, they make certain assumptions and develop criteria against which alternatives are evaluated for suitability. Unfortunately, much of this process is implicit, making later review difficult if not impossible. When requirements change, impacts on the design are difficult to trace. This can lead to costly rework or serious errors. We are developing Canard, an automated tool which uses possibility tables, constraints, and knowledge bases to assist in the generation of design alternatives consistent with goals and constraints. The facility also attempts to capture and document assumptions and tradeoffs made during the design process. We present an example which illustrates the use of Canard for a simple configuration problem. A more complex example traces the activity of a Boeing expert building a possibility table for robot arm design. Finally, the application of Canard to a NASA corporate memory facility project is described.