Formal verification of the correctness in hybrid expert systems

Abstract

It has been increasingly recognized over recent years that expert systems which combine one or more techniques greatly increase the problem solving capability and help overcome some of the shortcomings associated with any single technique. The verification of these expert systems requires methods which could tackle the multiple knowledge representation paradigms and integrated inference mechanisms used. The paper provides a formal description technique for verifying the correctness of hybrid expert systems (HES) that emphasizes an integration of object hierarchy, property inheritance and production rules. The main idea is to convert the HES into a state controlled coloured Petri net (SCCPN) where the object hierarchy, property inheritance and production rules are modelled as separated components in the same SCCPN. The detection and analysis of the anomalies in the system are done by constructing and examining the reachability tree spanned by the knowledge inference. This provides a formal basis for automating the deduction process and a means of verifying HES. A set of propositions is formulated to verify errors and anomalies in HES. Lastly, future extension of the approach is discussed.