ABSTRACT
Knowledge-based systems, or expert systems, are computer programs embodying knowledge about a narrow domain for solving problems related to that domain. An expert system usually comprises two main elements, a knowledge base and an inference mechanism. The knowledge base contains domain knowledge which may be expressed as any combination of “If-Then” rules, factual statements (or assertions), frames, objects, procedures, and cases. The inference mechanism is that part of an expert system which manipulates the stored knowledge to produce solutions to problems. Knowledge manipulation methods include the use of inheritance and constraints (in a frame-based or object-oriented expert system), the retrieval and adaptation of case examples (in a case-based expert system), and the application of inference rules such as
modus ponens
(If A Then B; A Therefore B) and
modus tollens
(If A Then B; Not B Therefore Not A) according to “forward chaining” or “backward chaining” control procedures and “depth-first” or “breadth-first” search strategies (in a rule-based expert system).
