The OWL Working Group at W3C invites implementation of its OWL 2 Web Ontology Language. OWL 2 is a compatible extension to OWL 1, providing additional features for people using ontologies. The OWL 2 document set contains 9 technical specifications and 4 instructional documents. The Recommendation-track specifications are now Candidate Recommendations, indicating that the Working Group and the W3C Director believe this is a good time for systems to begin adopting OWL 2 features on an experimental basis. The group maintains a list of implementations and encourages new information about implementations and other feedback to be sent to it comments address. The 4 instructional documents, which provide an introduction to OWL 2, are now at Last Call: overview, primer, new features and rationale, and quick reference. Finally, a new datatype used within both OWL and RIF, called rdf:PlainLiteral (formerly called rdf:text) is also a Candidate Recommendation.