In order to use in a computer system any information that is available in the real world from empirical observation, it is necessary to encode the information in some computer-usable format. For the most basic raw information such as numbers, strings of alphabets, and the like, this is a problem easily solved. However, as it gets increasingly desirable to use computer systems in sophisticated ways, it is likewise increasingly important to find ways to encode knowledge (as distinct from information). Knowledge may have many aspects, and is generally defined by a much higher degree of sophistication than bare information. Knowledge also is typically context-dependent by nature and importance.

The field of knowledge representation (abbreviated KR) is thus a broad-based one lying at the intersection of a number of distinct and important disciplines--philosophy, linguistics, psychology, computer science, cognitive science, and mathematical logic, and others. Usually, KR is...