The subfield of artificial intelligence concerned with designing and using systems for storing knowledge - facts and rules about some subject. A body of formally represented knowledge is based on a conceptualisATion - an abstract view of the world thAT we wish to represent. In order to manipulATe this knowledge we must specify how the abstract conceptualisATion is represented as a concrete dATa structure. An ontology is an explicit specificATion of a conceptualisATion. (1994-10-19)