The subfield of artificial intelligenceConCerned 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)