Explanation in mixed-initiative systems

Summary form only given. Mixed-initiative computer-aided design requires that the designer and the design system alternately take responsibility for elaborating a solution to a given set of requirements. For this to be possible, the system must be able to explain its actions to the user. A design support system written in a constraint-based logic programming language is described, and it is shown that the constraint network and truth maintenance system embedded in the language naturally support explanations of the kind required