BACKWARD INFERENCE SYSTEM

PURPOSE:To simplify the description of a rule and to improve the extendability of the rule by including an application rule ID expressing the application range of the rule, proposition and a requirement to describe the rule. CONSTITUTION:This backward inference system is provided with a backward inference control part 1 for controlling affirmative inference and negative inference and deciding the validity of proposition proof and a backward inference processing part 2 for proving a proposition and the processing part 2 includes an affirmative inference processing part 21 for executing affirmative proof and a negative inference processing part 22 for executing negative proof. In addition, a rule selecting part 3 for selecting an applicable rule in each of affirmative inference and negative inference, a fact base 4 for storing a fact and a rule base 5 for storing a rule for inference are also included in the system. A rule including an application rule ID expressing the application range of the rule, a proposition and a requirement is described and an affirmative rule and a negative rule are alternately and reculsively applied. Thus the rule description can be simplified and the extendability and generality of rules can be improved.