Abstract:In this article we describe how two popular AI representation techniques—frames and production systems— can be usefully combined under a general AI object‐oriented approach to problems which arise in the domain of hardware fault diagnosis. One of the main advantages of such a combination is that causal reasoning— crucial to the domain under consideration — can also be naturally and effectively represented. In order to put the combination of frames and production systems on a sound methodological footing, we first provide a knowledge engineering methodology which is an object‐oriented re‐interpretation of ontolog