Formal approaches to rule-based systems in medicine: The case of CADIAG-2

There is no established formal framework for expert systems based on weighted IF–THEN rules. We discuss three mathematical models that have been recently proposed by the authors for CADIAG-2—a well-known system of this kind. The three frameworks are based on fuzzy logics, probability theory and possibilistic logic, respectively. CADIAG-2 is used here as a case study to evaluate these frameworks. We point out their use, advantages and disadvantages. In addition, the described models provide insight into various aspects of CADIAG-2.

► We discuss three different formal frameworks for the expert system CADIAG-2.
► The three frameworks are based on t-norm based logics, probability theory and possibilistic logic.
► We point out their advantages and disadvantages.
► We show how to use the frameworks based on t-norm based logics and probability theory for checking the system’s rules.
► Our frameworks also provide insights into various aspects of CADIAG-2.