Director: An Interpreter for Rule-based Programs

Programs interacting with users via natural language interfaces generally require more sophisticated control structures than those needed by programs interacting with users through less flexible mechanisms. This paper describes our development of Director, an interpreter (inference engine) for rule-based programs. Providing an efficient combination of forward and backward chaining, heuristic and user control of inference, and ready access to portions of its internal structure, Director facilitates the construction of systems with natural language interfaces as well as other rule-based systems in which queries are expensive