OWL is an acronym for Web Ontology Language, a markup language for publishing and sharing data using ontologies on the Internet. OWL is a vocabulary extension of the Resource Description Framework (RDF) and is derived from the DAML+OIL Web Ontology Language (see also DAML and OIL). Together with RDF and other components, these tools make up the Semantic Web project.
OWL represents the meanings of terms in vocabularies and the relationships between those terms in a way that is suitable for processing by software.
The OWL specification is maintained by the World Wide Web Consortium (W3C).
OWL currently has three flavors: OWL Lite, OWL DL, and OWL Full. These flavors incorporate different features, and in general it is easier to reason about OWL Lite than OWL DL and OWL DL than OWL Full. OWL Lite and OWL DL are constructed in such a way that every statement can be decided in finite time; OWL Full can contain endless 'loops'