Checking an Expert Systems Knowledge Base for Consistency and Completeness

Abstract

In this paper we describe a program that verifies the consistency and completeness of expert system knowledge bases which utilize the Lookheed Expert System (LES) framework. The algorithms described here are not specific to LES and can be applied to most rule-based systems. The program, called CHECK, combines logical principles as well as specific information about the knowledge representation formalism of LES. The program checks for redundant rules, conflicting rules, subsumed rules, missing rules, circular rules, unreachable clauses, and deadend clauses. It also generates a dependency chart which shows the dependencies among the rules and between the rules and the goals. CHECK can help the knowledge engineer to detect many programming errors even before the knowledge base testing phase. It also helps detect gaps in the knowledge base which the knowledge engineer and the expert might have overlooked. A wide variety of knowledge bases have been analyzed using CHECK.