"Ontology" is a term increasingly used in all areas of computer and information science to denote, roughly, a hierarchically organized classification system associated with a controlled, structured vocabulary that is designed to serve the retrieval and integration of data. An ontology under this view is an artifact whose purpose is to ensure that information about entities in some domain is communicated successfully from one context to another, and this despite differences in opinions about what is the case in that domain or differences in the terminology used by the authors to describe the entities it contains.