CO-STATES, CONSTRAINTS, AND DIAGRAMMATIC REASONING

State space search is the most fundamental concept in artificial intel ligence (AI). In this paper we examine the notion of co-state for prob lem solving. To understand the rationale of this extension, we describ e two applications which employ the co-state concept, namely, expert s ystem explanation and detective story analysis. We also argue how co-s tates can be related to the studies of constraints and diagrammatic re asoning.