OWL 2 Web Ontology Language: structural specification and functional-style syntax

TLDR

OWL 2 is a formally defined ontology language for the Semantic Web that provides classes, properties, individuals, and data values, and is primarily exchanged as RDF documents. OWL 2 defines its constructs structurally and offers a functional‑style syntax, enabling reasoning under either RDF‑Based or Direct Semantics, with Direct Semantics support for OWL 2 DL ontologies via established techniques.

Abstract

The OWL 2 Web Ontology Language, informally OWL 2, is an ontology language for the Semantic Web with formally defined meaning. OWL 2 ontologies provide classes, properties, individuals, and data values and are stored as Semantic Web documents. OWL 2 ontologies can be used along with information written in RDF, and OWL 2 ontologies themselves are primarily exchanged as RDF documents. The OWL 2 Document Overview describes the overall state of OWL 2, and should be read before other OWL 2 documents. The meaningful constructs provided by OWL 2 are defined in terms of their structure. As well, a functional-style syntax is defined for these constructs, with examples and informal descriptions. One can reason with OWL 2 ontologies under either the RDF-Based Semantics [OWL 2 RDF-Based Semantics] or the Direct Semantics [OWL 2 Direct Semantics]. If certain restrictions on OWL 2 ontologies are satisfied and the ontology is in OWL 2 DL, reasoning under the Direct Semantics can be implemented using techniques well known in the literature.