"Protégé is a free, open source ontology editor and knowledge-base framework
The Protégé platform supports two main ways of modeling ontologies via the Protégé-Frames and Protégé-OWL editors. Protégé ontologies can be exported into a variety of formats including RDF(S), OWL, and XML Schema." -- Protege Home Page (viewed 30 October 2012)
