Artificial intelligence is the study of the simulation of human cognitive faculties. Applications of various aspects of AI are important to the development of expert or knowledge-based systems. An individual expert system can be characterized by the methods selected for representing expertise, transfer of expertise and user interaction. Various aspects of a domain can be represented by separate knowledge sources acquired from different experts or through different models of reasoning. Combination of these knowledge sources can improve the capability or robustness of a model of a domain. The literature of clinical and experimental psychology contains much research relevant to the problem of improving the communication between knowledge engineers and domain experts. Specifically, the Personal Construct Theory of George A. Kelly (1955) has served as the basis for several recent experimental approaches to the design and construction of automated (i.e., computer-based) knowledge acquisition tools. A measure of the shared aspects of domain knowledge common to multiple experts is developed and illustrated with this model using knowledge gathered about two different domains. A model of the shared aspects of personal construct systems of a domain is developed and a system to draw conclusions based upon this information is also proposed