Knowledge systems: Principles and practice

We describe what is expected of a knowledge-based expert system, and the components from which such a system is constructed. We give a view of how an interplay between principles and practice has helped the knowledge system field to develop, and we give simple examples to show that reasoning techniques based on formal logic are now starting to provide a useful coupling between scientific and engineering work in the field. The examples are about logic programming, knowledge representation, judgmental reasoning, and about three methods by which a system can acquire the knowledge it needs.