Useful as it is however, the NCI Metathesaurus is not well suited to serve as a coding nomenclature1 . The hierarchies of the NCI terminology in NCI Metathesaurus are not true IS_A hierarchies, for example. The NCI Thésaurus, which became operational in late 2001, is designed to address this need. It is intended for NCI offices and divisions to use the Thésaurus as a source of codes associated with terminology concepts to annotate data and other information artifacts and facilitate information retrieval. The NCI Thésaurus is not yet a true ontology2 , as it contains numerous primitive concepts. It.
