Different ontology languages are often based on different underlying paradigms (e.g., description logic, first-order logic, frame-based representation, taxonomy, semantic net, and thesaurus). Some ontology languages are very expressive and some are not. Some ontology languages have a formally defined semantics and some do not. Some ontology languages have inference support and some do not. If we are to allow all these different languages, then we are faced with the very challenging problem of translating between them.