Rule chaining in fuzzy expert systems

Lawrence O. Hall Dept. of Computer Science and Engineering, ENB 118 University of South Florida Tampa, Fl. 33620 [email protected] Abstract A fuzzy expert system must do rule chaining differently than a non-fuzzy expert system. In particular, any rule that can fire with a particular linguistic variable in its consequent must fire before any rule whose antecedent conditions depend upon the resultant fuzzy set value of the consequent linguistic variable 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, and Kak points out that a version of 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 several approaches to obtaining the desired behavior in FuzzyCLIPS. Further, a potential pitfall with the FuzzyShell approach to dealing with chaining is pointed out.