Abstract: The present invention is an expert system with a plurality of independent knowledge bases, including a process and apparatus for employing an inference engine to select one of the knowledge bases based on one or more key factors. In particular, an embodiment using a batch mode for input of data to the expert system is disclosed, based on which, one of the stored independent knowledge bases is selected and employed in connection with the inference engine. This expert system has application to maintenance of a document processing system, where one of several types of maintenance is selected, causing a respective knowledge base or set of rules to be selected.