Ontologies are set to play a key role in the ”Semantic Web”, extending syntactic interoperability to semantic interoperability by providing a source of shared and precisely defined terms. DAML+OIL is an ontology language specifically designed for use on the web; it exploits existing web standards (XML and RDF), adding the familiar ontological primitives of object oriented and frame based systems, and the formal rigor of description logics (DLs). The logical basis of the language means that reasoning services can be provided, both to support ontology design and to make DAML+OIL described web resources more accessible to automated processes [2].