Abstract: Disclosed is a processing apparatus capable of optimizing its rule base comprising a plurality of rules having an antecedent and a consequent each. The antecedent contains input conditions of machining, and the consequent describes the result of machining. The antecedents are applied to input condition data. The consequents of the applied rules yield machining result data that are evaluated for rule fitness. When the rule base is updated, some rules are deleted and some preserved depending on their degrees of fitness. Between given two rules having the same consequent, any number of corresponding conditional elements in their antecedents are exchanged so as to generate new rules. The process is repeated until the rule base is optimized. With the antecedents of rules applied to input condition data and with the consequents of the applied rules yielding machining result data, those data may be modified according to modification request data.