Shared sets of explicitly defined terminology which provide a deeper level of meaning by providing equivalence relations between terms. Ontologies describe concepts rather than words.
Dictionary.com: The branch of metaphysics that deals with the nature of being.
An ontology is "the specification of one's conceptualization of a knowledge domain." and is therefore a form of knowledge representation. It is the specs that formally defines relations among terms, eg., taxonomy and set of inference rules. Together they form a richer description of relationships between terms. A formal ontology is a controlled vocabulary expressed in an ontology representation language.
Ontology Inference Layer
This is a proposal for a web-based representation and inference layer for ontologies, which combines the widely used modelling primitives from frame-based languages with the formal semantics and reasoning services provided by description logics.
- What is an Ontology?
- Formal Ontology, Conceptual Analysis and Knowledge Representation by Nicola Guarino at Citeseer