Expert systems, computer programs that combine knowledge from a specific domain with a general reasoning mechanism (inference engine) are a booming area. Successful applications are reported from a broad variety of industries: medicine, chemical industry, computer industry, financial and insurance companies, accounting firms, and many others (Feigenbaum, McCorduck, and Nil, 1988). Applications have taken place in several functional areas of management: operations management, procurement, resource allocation, inventory management, project management, financial decision-making, and accounting (Silverman, 1987).