Expert system wtih a plurality of independent knowledge bases

Claim 1

An expert system for controlling maintenance on a machine requiring periodic maintenance; an inference engine for processing an input and generating an output including a prioritized list of maintenance activities based on a set of rules related to the maintenance activities on the machine; a plurality of stored sets of rules relating to maintenance of the machine and prioritization of such maintenance; an input including a key factor relating to the maintenance of the sorting machine, each value of the key factor having associated with it one set of stored rules, said key factor chosen from tolerant, normal and strict and the set of stored rules includes a tolerant set of maintenance rules, a normal set of maintenance rules and a strict set of rules; and means responsive to said key factor for selecting the associated set of stored rules for processing by the inference engine and for generating a prioritized list of maintenance activities based on the key factor, whereby the inference engine uses the selected set of rules to process the input and generate an output indicative of maintenance to be performed on the machine.