The SIOC initiative (Semantically-Interlinked Online Communities) aims to enable the integration of online community information. SIOC provides a Semantic Web ontology for representing rich data from the Social Web in RDF. It has recently achieved significant adoption through its usage in a variety of commercial and open-source software applications, and is commonly used in conjunction with the FOAF vocabulary for expressing personal profile and social networking information. By becoming a standard way for expressing user-generated content from such sites, SIOC enables new kinds of usage scenarios for online community site data, and allows innovative semantic applications to be built on top of the existing Social Web. The SIOC ontology was recently published as a W3C Member Submission, which was submitted by 16 organisations.
In this website you can find information about folksonomies, their strenghts and weaknesses, and Sem4Tags an approach to improve multilingual folksonomies using semantic web techniques. In addition, there is information about the developed demo software to associate tags with semantic entities.
The Citation Typing Ontology (CiTO) is an ontology, written in OWL 2 DL, to enable characterization of the nature or type of citations, both factually and rhetorically, and to permit these descriptions to be published on the Web.
F. Baader, B. Ganter, B. Sertkaya, und U. Sattler. Proceedings of the 20th international joint conference on Artifical intelligence, Seite 230--235. San Francisco, CA, USA, Morgan Kaufmann Publishers Inc., (2007)