Protégé is a free, open source ontology editor and knowledge-base framework. The Protégé-OWL plug-in extends Protégé to support the Web Ontology Language (OWL). Visit the [Protégé] page for more information.

NCI Protégé is a collection of Protégé plug-ins developed for the NCI-specific editing environment and used to edit the NCI Thesaurus. NCI Protégé provides a customized OWL editing environment, including additional editing and querying capabilities that are not available in the Protégé OWL plug-in. The NCI-specific plug-ins have been implemented as a tabbed interface.