Ontologies (vocabularies)

Formal, machine-readable specifications of a conceptual model, in which concepts, properties, relationships, functions, constraints, and axioms are all explicitly defined. Refers to a compilation that is not technically a controlled vocabulary, but that uses one or more controlled vocabularies for a defined domain and expresses the vocabulary in a representative language that has a grammar for using vocabulary terms to express something meaningful. Ontologies generally divide their world into the following areas: individuals, classes, attributes, relations, and events. The grammar of the ontology links these areas together by formal constraints that determine how the vocabulary terms or phrases may be used together.