Compositional Verification of Knowledge-Based Systems: A Case Study for Diagnostic Reasoning

In this paper a compositional verification method for models of knowledge-based systems is introduced. Required properties of the system are formally verified by deriving them from assumptions that themselves are properties of sub-components, which in their turn may be derived from assumptions on sub-sub-components, and so on. The method is based on properties that are formalised in terms of temporal semantics; both static and dynamic properties are covered. The compositional verification method imposes structure on the verification process. By the possibility to focus at one level of abstraction (information and process hiding), compositional verification provides transparency and limits the complexity per level. Since verification proofs are structured in a compositional manner, they can be reused in case of modification of the system. The method is illustrated for a generic model for diagnostic reasoning.