Definition: Ontology

by Jack Krupansky

(1) An ontology is a specification of a domain, of all that 'exists' in a domain, including terms, concepts, entities, axioms, theorems, laws, rules, and the actions than can be performed on everything within the domain as well as how to reason about the domain.

A software agent can have an ontology for the domain consisting of itself, as well as ontologies for the domains with which the agent wishes to interact or reason, including other agents, data sources, services, and conceptual domains that the agent wishes to reason about.

Entities within a domain can be clustered into a taxonomy based on common characteristics.

Sometimes confused with a taxonomy, which is simply a hierarchical categorization or classification of entities.

(2) Ontology is the science of describing the kinds of entities in the world and how they are related. [See W3C OWL Web Ontology Language Guide.]

(3) An ontology is a collection of concepts represented as Semantic Web resources (typically classes of resources) and RDF statements about those concepts (classes of resources) which represent properties, constraints, and relationships between those concepts (classes), that enable computer software applications and software agents to reason about those concepts, both at the class and instance levels.

Synonym for domain theory.