Ontologies : Domain Presentation
In the context of knowledge
representation and reasoning, the term ontology means a
specification of a conceptualization
An ontology is therefore a description of the concepts
that exist or can exist in a particular domain as well
as of the relationships in which the various concepts
Ontologies are designed for knowledge
sharing since they provide the common vocabulary (or
description space) for a set of agents, either human or
software. Therefore, they have a consensual character,
although there is no need for a particular ontology to
be the product of a universal consensus (personal
ontologies may exist).
Examples of existing large scale
ontologies are WordNet 
and Cyc .
Large, electronically stored and
accessible-through-web ontologies are the backbone of
the Semantic web. Although there may be ontologies
described in a wide range of languages, two of those
languages are en route to become standards: RDF(S) 
and OWL .
Dan Brickley and Ramanathan Guha.
Resource Description Framework (RDF) Schema
Specification 1.0. Recommendation, W3C, 2000.
Mike Dean and Guus Schreiber (eds.). OWL
web ontology language: reference. Recommendation,
 Thomas R. Gruber, Toward principles for the design
of ontologies used for knowledge sharing, International
Journal of Human-Computer Studies, 43(5-6):907-928,
Douglas B. Lenat. Cyc: A Large-Scale
Investment in Knowledge Infrastructure. The
Communications of the ACM 38(11):33-38, 1995.
George Miller. WordNet: A lexical
database for English. Communications of the ACM,