The W3C OWL Working Group has published new Working Drafts for OWL 2, a language for building Semantic Web ontologies. An ontology is a set of terms that a particular community finds useful for organizing data (e.g., for data about a book, useful terms include “title” and “author”). OWL 2 (a compatible extension of “OWL 1″ ) consists of 13 documents (7 technical, 4 instructional, and 2 group Notes). For descriptions and links to all the documents, see the ” OWL 2 Documentation Roadmap.” This is a “Last Call” for the technical materials and is an opportunity for the community to confirm that these documents satisfy requirements for an ontology language. This is a second Last Call for six of the documents, but because the changes since the first Last Call are limited in scope, the review period lasts only 21 days. For an introduction to OWL 2, see the four instructional documents: an “overview,” “primer,” “list of new features,” and “quick reference.”,