The “Semantically-Interlinked Online Communities Ontology”, better known as SIOC, is now an official member submission of W3C, i.e., it has a stable version stored on the W3C’s website. From the abstract of the submission:
The SIOC (Semantically-Interlinked Online Communities) Core Ontology provides the main concepts and properties required to describe information from online communities (e.g., message boards, wikis, weblogs, etc.) on the Semantic Web. This document contains a detailed description of the SIOC Core Ontology.
The submitters included DERI Galway, DFKI, FhG-FZI, CTIC, OpenLink Software Inc., Opera Software, STFC, UPM, and University of Trento.