Battling Scylla and Charybdis: the search for redundancy and ambiguity in the 2001 UMLS metathesaurus.

I previously developed methods for identifying cases of multiple synonymous concepts (redundancy) and concepts with multiple meanings (ambiguity) and applied them to the 1995 UMLS Metathesaurus. These methods use semantic approaches (including knowledge about word synonymy and the semantic types assigned to concepts) to complement the standard lexical approaches. In this paper, I describe the results of their application to the 2001 Metathesaurus and examine their implications for the evolution of the UMLS.