In this short case study we have shown how thesauri differ from RDFS and OWL ontologies. We have shown on a simple example the growing expressiveness of the languages from thesauri to RDFS to finally OWL evolving from a simple thesaurus model to a more complex OWL ontology model. Whereas thesauri provide only very basic modelling paradigms and no knowledge can be extracted from a thesaurus except mere simple keyword relationships, OWL allows for powerful knowledge modelling and inference by offering a vast variety of features. Moreover, thesauri are mostly stored in proprietary databases without standard exchange formats or procedures, whereas OWL is a W3C recommendation, encoded in XML and therefore allows for perfect interoperability on the web.
