Pattern-Directed Invocation with Changing Equations

Abstract

The interaction of pattern-directed invocation with equality in an automated reasoning system gives rise to a completeness problem. In such systems, a demon needs to be invoked not only when its pattern exactly matches a term in the reasoning data base, but also when it is possible to create a variant that matches. An incremental algorithm has been developed which solves this problem without generating all possible variants of terms in the database. The algorithm is shown to be complete for a class of demons, called transparent demons, in which there is a well-behaved logical relationship between the pattern and the body of the demon.