2. A fuzzy inference apparatus, comprising: an input device for entering input data relating to phenomena; a storage device for storing knowledge of expert users expressing relationships between phenomena and conclusions as a plurality of membership functions, whereby said relationships can include a case in which a single phenomenon, for which a single conclusion is to be drawn, has two or more separate definitions which are conjoined in an OR relationship, said two or more definitions being represented by at least two membership functions; a grade calculating device for calculating a grade measure of said input data with respect to each of said plurality of membership functions for a given conclusion, wherein when a single phenomenon, for which a conclusion is to be drawn, has two or more separate definitions which are conjoined in an OR relationship, a grade measure of said input data is produced for each of said two or more of membership functions representing said two or more definitions; a fuzzy information amount calculating device for calculating a fuzzy information amount for each said phenomenon using said grade measures; and a possibility calculating device for performing fuzzy inferences to determine a possibility of a conclusion using said grade measures and said fuzzy information amounts.
2. A fuzzy inference apparatus, comprising: an input device for entering input data relating to phenomena; a storage device for storing knowledge of expert users expressing relationships between phenomena and conclusions as a plurality of membership functions, whereby said relationships can include a case in which a single phenomenon, for which a single conclusion is to be drawn, has two or more separate definitions which are conjoined in an OR relationship, said two or more definitions being represented by at least two membership functions; a grade calculating device for calculating a grade measure of said input data with respect to each of said plurality of membership functions for a given conclusion, wherein when a single phenomenon, for which a conclusion is to be drawn, has two or more separate definitions which are conjoined in an OR relationship, a grade measure of said input data is produced for each of said two or more of membership functions representing said two or more definitions; a fuzzy information amount calculating device for calculating a fuzzy information amount for each said phenomenon using said grade measures; and a possibility calculating device for performing fuzzy inferences to determine a possibility of a conclusion using said grade measures and said fuzzy information amounts. 3. The fuzzy inference apparatus of claim 2, wherein said grade calculation performed by said grade calculation device is a MAX calculation.