Knowledge base verification

Publisher Summary This chapter describes several tools and techniques for validating a knowledge base, with emphasis on the rule checker. The other tools, such as the syntax checker and test case manager, also help the knowledge engineer to maintain the correctness of one's knowledge base and of the tool one is using. From the experiences with constructing different knowledge bases, one fined that many changes and additions are made during the development and maintenance of a knowledge base. The most frequent problems that CHECK has detected are unreachable and dead-end clauses. These types of errors are difficult to detect with conventional knowledge base debugging aids. It is found that redundant and conflicting rules appeared the least often. Nevertheless, CHECK'S automated facilities have saved engineers from many hours of tedious debugging. As the field of knowledge-based systems matures, large expert systems will be fielded in critical situations. As it will be impossible to test all paths beforehand, one must have assurance that deadly traps, such as circular rules and dead-end clauses do not exist in the knowledge base. Thus, verification facilities similar to the ones described in this paper becomes essential.