Chaining in fuzzy rule-based systems

A fuzzy expert system must do rule chaining differently than a non-fuzzy expert system. In particular, all rules that can fire with a particular linguistic variable in their consequent must fire before any rule whose antecedent conditions depend upon the resultant fuzzy set value is allowed to fire. The dependent rules would be considered in a chain with the fuzzy rules which generate or assert the needed fuzzy linguistic variable. A recent paper by Pan-DeSouza-Kak (1998) points out that the FuzzyCLIPS expert system shell does not operate with chained fuzzy rules as one would expect. They introduce FuzzyShell which is described as the only known shell to have the expected fuzzy rule chaining performance. In this paper, we show how FuzzyCLIPS can be made to have the required property. Further, a potential pitfall with the FuzzyShell approach to dealing with chaining is pointed out