Rule validation based on logical deduction

Expert systems and deductive database systems are knowledge-based systems which have the capability of storing andproeessing datartndknowledge rules, and performing logical deductions. The knowledge bases of these systems are usually assumed to be eonsisten~ that is, no contradictions are deduced by the system. This assumption is not realistic since, in real-world applications, a knowledge base can contain a large number of rules which pose problems in terms of their ecmsistency. Thus, an automatic knowledge validation procedure is necessary for building a reliable knowledge-based system. In this paper, we present a knowledge validation technique based on the resolution principle to detect inconsistencies of a knowledge base. In this work, we formally define the eoneept of rule base inconsistency and show its relationship with the concept of unsatisfiability in formal logic. We also define completeness of a rule validation algorithm and show that our rule validation method is complete in the sense that it can not only identify all the input facts casing the system to deduee contradictions but also determine the specific subset of rules involved in the deductions of the contradictions. Based on this information, knowledge base designers can then make proper corrections to their knowledge base designs. A rule validation system using the proposed technique has been implemented in Prolog.