PlatypusWiki is an ongoing project that started on 23 December 2003. It is an enhanced wiki with ideas taken from SemanticWeb. They have called it a Wiki:SemanticWikiWikiWeb. It offers a simple user interface to create a wiki page plus metadata according with W3C standards. It uses ResourceDescriptionFramework (RDF), RDF Schema, and OWL (Web Ontology Language) to create ontologies and manage metadata.
See also RdfForWikis.
Other interesting features: