Combining Model-Based and Case-Based Expert Systems

In discussing diagnostic expert systems, the merits of model-based systems vs. case-based systems are often debated. In this chapter, we show that the two are not mutually exclusive. To the contrary, they complement each other. Based on our research with the ATTEST diagnostics expert system, we present an approach of combining the two reasoning mechanisms (in addition to other mechanisms) into one integrated system. Depending on the knowledge available, the cases available, and time and cost considerations, the system leaves it up to the user to decide on the relative proportion of case-based to model-based he/she wishes to employ in any given situation.