A Software Engineering Methodology for Rule-Based Systems

Current expert systems are typically difficult to change once they are built. This paper introduces a method for developing more easily maintainable rule-based expert systems, which is based on dividing the rules into groups and focusing attention on those facts that carry information between rules in different groups. It describes a new algorithm for grouping the rules of a knowledge base automatically and a notation and set of software tools for the proposed method. The approach is supported by a study of the connectivity of rules and facts in rule-based systems, which found that they indeed have the latent structure necessary for the programming methodology, as well as by recent experimental results. In contrast to the homogeneous way in which the facts of a rule-based system are usually viewed, this approach distinguishes certain facts as more important than others with regard to future modifications of the rules.