A software engineering approach to the design of a medical expert system

Presents a case study of the use of formal specification techniques in the design of a knowledge-based system. The Z specification notation is used in the development of a medical flow chart program, beginning with a highly abstract notion of inference and proceeding by refinement toward a particular implementation for flow charts. Diagnostic inference is modelled by idempotent decreasing functions. The flow chart was found to be significantly more accurate than a statistical classifier (independence Bayes). Formal specification provides several benefits. Design decisions are made explicit and are documented concisely, and the results of making alternative choices can be explored within the same framework. The formal specification also suggests approaches that probably would not otherwise have been considered