The Unified Medical Language System (UMLS) contains medical terms and the semantics between them. The terms have roots in about 100 heterogeneous concept-based classification systems and medical vocabularies in 15 languages at present. The long term project was started at the end of 1980 by the US National Library of Medicine (NLM). The project wants to: improve and to link the numerous concept-based classification systems up with one another semantically, and in this fashion, help to create conceptual links between user queries and pertinent specialised information as well as improve the accessibility of heterogeneous online information systems.
UMLS consolidates terms from specific vocabularies to a concept-based Metathesaurus. Concepts from the Metathesaurus are linked in a semantic network and feed a linguistic lexicon, which - together with computer programs for natural language processing - forms the Specialist Lexicon of the UMLS.
There is an abundance of basic and further information concerning this thesaurus on the UMLS-web pages of the NLM.
DIMDI supplies the UMLS with a large amount of German-language vocabularies thereby making German the second most frequent language in the Metathesaurus. Since the German-language entries are stored in the Metathesaurus without umlauts and diacritics, their use in computer systems is somewhat limited.
The following German-language vocabularies are part of the Metathesaurus: