The W3C OWL Working Group has published a working draft of OWL 2 Web Ontology Language Document Overview:
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.
This document, part 1 of 13 in the OWL 2 document set, serves as an introduction to OWL 2 and the various other OWL 2 documents. It describes the various syntaxes for OWL 2, the different kinds of semantics, the defined profiles (sub-languages), and the differences between OWL 1 and OWL 2.