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

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.