1. A knowledge engineering tool for use by an expert system user in conjunction with a photofinishing process incorporating a control strip for providing diagnostic information concerning said process, said tool comprising: (a) a target expert system; (b) means for inputting into said target expert system target data obtained from analysis of said control strip used in said photofinishing process for allowing said target expert system to look for any deviations from the norm in said target data; (c) a target knowledge base module; (d) means for inputting into said target knowledge base module additional data relating to said photofinishing process; (e) a data definition module; (f) means for inputting into said data definition module structural knowledge relating to a photofinishing process; (g) an expert system skeleton module that contains structural knowledge along with requested data from said target knowledge base module and structural knowledge existing within said data definition module to provide a list of symptoms characterizing said process to the expert system user; (h) means for generating a first list of possible causes of any deviation from normal and an indication of the occurrance of said causes based upon the system characterization of this particular process; and (i) means for generating a second list of prescriptions for alleviating each of the possible causes in said first list.