The upcoming next generation of the internet, often referred to as the Semantic Web, will bring a lot of new technologies, one of which is the Web Ontology Language (OWL). One feature of this language is to support interoperability between software applications, including web services and intelligent agents. Another technology to bring interoperability between software programs is ISO-10303 Standard Exchange of Product data (STEP). The Industry Foundation Classes (IFC) have been developed as a building information model for the building and construction industry using technology from STEP. Converting IFC to OWL can be done on different ways. A unidirectional conversion from an IFC to an OWL has been developed for research purposes. The developed prototype converts not all the IFC data to OWL but supports the search for a more appropriate mapping. As the conversion is not straightforward, reengineering the building model to gain more advantages of functionality offered by OWL has to be...