Bi-directional Search for Bugs: A Tool for Accelerating Knowledge Acquisition for Equation-Based Tutoring Systems

Authoring the knowledge base for an intelligent tutoring system (ITS) is difficult and time consuming. In many ITS, the knowledge base is used for solving problems, so authoring it is an instance of the notoriously difficult knowledge acquisition problem of expert systems. General tools for knowledge acquisition have shown only limited success, which suggests developing tools that apply only to specific kinds of knowledge bases. Pyrenees is an ITS whose knowledge base is composed mostly of conditioned equations. We have developed several tools for authoring Pyrenees knowledge bases. This paper focuses on a novel and particularly powerful tool that uses bidirectional search to locate bugs in the knowledge base. In several evaluations, human authoring was significantly faster when the tool was available than when it was unavailable