1989 Reports

User-Defined Predicates in OPS5: A Needed Language Extension for Financial Expert Systems

Pasik, Alexander J.; Miranker, Daniel P.; Stolfo, Salvatore; Kresnicka, Thomas

OPS5 is widely used for expert system development in industry as well as for academic research. Its limited expressive power, however, can lead to cumbersome and inefficient code. Often a single domain rule must be encoded as a series of OPS5 rules requiring extensive performance overhead and resulting in an awkward representation of the knowledge. In the financial expert system ALEXSYS, which performs mortgage pool allocation, the lack of user-defined predicates proved to be a major obstacle, prohibiting real time performance. This work describes the addition of user-defined predicates in OPS5, supported by a patch to Carnegie-Mellon University's Common lisp OPS5 implementation. Also, the necessity of this extension is demonstrated in the context of the ALEXSYS mortgage pool allocation expert system, both in terms of increased efficiency and improved knowledge representation.