In creating an ontology that represented these semantics, the first choice was to decide among OWL's three sub-languages: OWL Lite, OWL DL, and OWL Full[2]. Though OWL Full is the most expressive of the three languages, the first two have several advantages. OWL DL and its formal subset, OWL Lite, are guaranteed to be both computationally complete and decidable. The NCI Thésaurus is created using a DL tool, so the restrictions of these two variants of the .