EVID: A system for interactive defeasible reasoning

Abstract I describe a system for interactive, automated defeasible reasoning. An application program using this system can infer a conclusion defeasibly from a conjunction of supporting facts together with an appropriate general rule. This particular inference of the conclusion might be defeated by additional facts, although other independent evidence could still support the conclusion on the basis of other rules. The system has been implemented in Prolog, and includes an extensive logical interface that permits the user to interact with and override an application program's defeasible conclusions, subject to certain constraints on the user's consistency. Applications to decision support systems are described.