I. Introduction
Interest in fuzzy inference has been stimulated by the improving processing capabilities of computer hardware. Fuzzy inference is the process of formulating human subjective cognition and is based on IF-THEN rules. We expected that fuzzy inference would re-create the subjective judgments of professionals. In this context, IF-THEN rules can be said to contain the knowledge and skill of professionals. The IF-THEN rules, however, tend to take a rudimentary form by means of simplification.