A property represented in CML (top) and the equivalent RDF (bottom)-as used in the Quixote repository . The dictionary is referenced by compchem:hfenergy for which there must be an entry in an online dictionary. These are completely equivalent and can be translated in both directions without semantic loss. (There are minor syntactic variants such as the capitalization varying systematically.) It is always possible to generate RDF from CML; the reverse may not be possible for arbitrary RDF. The challenge is to create communally acceptable dictionaries/ontologies-the syntax (CML or RDF) is immaterial.