Knowledge engineering the UMLS.

In order to transform a major portion of the Unified Medical Language System (UMLS) into a formally sound description logics system we have developed a four-step knowledge engineering approach. We report on experiments with a Loom knowledge base which consists of 164,000 concepts and 76,000 relations covering human anatomy and pathology. We discuss the fully automatized as well as interactive semiautomatic steps. The latter ones focus on the manual work necessary to render the formal target representation structures complete and adequate.