Experiences with an expert system for odes

An Expert System can be defined “bottom up” as a software package that uses a knowledge base and inference engine, or “top down” as one that attempts to simulate the reasoning of a human expert. PLOD, a package for solving systems of ordinary differential equations satisfies the second form of the definition but not the first. We describe the major features of the package, and how we have been forced to “reinvent the wheel” in order to provide needed capabilities. Certain standard building blocks are described in the hope that these can be developed for use in other systems.