The Resource Description Framework (RDF), together with its extension RDF Schema, is a logical formalism that allows formalizing information models in the form of RDF vocabularies and representing propositional information on the Web, embedded in web pages or in the form of special web data sources. OWL extends RDF by adding many additional language elements for expressing constraints, equalities and derived classes and properties in the context of defining vocabularies. Unfortunately, both RDF and OWL have many usability issues.