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United States National Library of Medicine National Institutes of Health

Fact Sheet
Unified Medical Language System®


Purpose:

The purpose of NLM's Unified Medical Language System ® (UMLS ® ) is to facilitate the development of computer systems that behave as if they "understand" the meaning of the language of biomedicine and health. To that end, NLM produces and distributes the UMLS Knowledge Sources (databases) and associated software tools (programs) for use by system developers in building or enhancing electronic information systems that create, process, retrieve, integrate, and/or aggregate biomedical and health data and information, as well as in informatics research. By design, the UMLS Knowledge Sources are multi-purpose. They are not optimized for particular applications, but can be applied in systems that perform a range of functions involving one or more types of information, e.g., patient records, scientific literature, guidelines, public health data. The associated UMLS software tools assist developers in customizing or using the UMLS Knowledge Sources for particular purposes.

UMLS Knowledge Sources and Software Tools:

There are three UMLS Knowledge Sources: the Metathesaurus ® , the Semantic Network, and the SPECIALIST lexicon. They are distributed with flexible lexical tools and the MetamorphoSys install and customization program.

The Metathesaurus provides a uniform, integrated distribution format for more than 100 biomedical and health-related vocabularies, classifications, and coding systems (some in multiple languages) and links many different names for the same concepts. The Metathesaurus includes vocabularies and coding systems designated as standards for the electronic exchange of administrative and clinical data in the United States, including SNOMED CT ® , LOINC ® , and RxNorm. The Semantic Network contains information about the types or categories (e.g., "Disease or Syndrome", "Virus") to which all Metathesaurus concepts have been assigned and the permissible relationships among these types (e.g., "Virus" causes "Disease or Syndrome"). The SPECIALIST lexicon contains syntactic information for many terms and component words that appear in the Metathesaurus or other biomedical sources, as well as common English words, including verbs, that do not appear in the Metathesaurus. The associated lexical tools allow users to abstract away from the many types of linguistic variation that appear in natural language. MetamorphoSys, a multi-platform Java program, must be used to install the UMLS Knowledge Sources in local systems. It also can be used to produce the pre-defined or custom subsets of the Metathesaurus that are generally required for efficient use in local systems.

UMLS Applications:

NLM and many other institutions apply the UMLS resources in a wide variety of Applications including information retrieval, natural language processing, creation of patient and research data, and the development of enterprise-wide vocabulary services. NLM's applications include PubMed ® , the NLM Gateway, ClinicalTrials.gov , and the Indexing Initiative. Other examples of UMLS-enabled applications include the National Cancer Institutes Enterprise Vocabulary Services and the Agency for Healthcare Research and Qualitys National Guidelines Clearinghouse and National Quality Measures Clearinghouse.

A bibliography of UMLS journal articles from PubMed/MEDLINE covering 1997 to the present in the form of search results may easily be obtained by clicking here. An older bibliography of UMLS articles including a variety of media is available by clicking Comprehensive Bibliography 1986-1999.

Obtaining the Knowledge Sources:

The UMLS resources are available free to U.S. and international users. Requestors must complete a License Agreement for the Use of the UMLS Metathesaurus which is an online Web-based process. Licensees are responsible for complying with the restrictions on use of the contents of the UMLS Metathesaurus detailed in the agreement. Once the license agreement is in place, much of the content of the Metathesaurus may be used under very "open" conditions. However, some uses of some vocabularies contained in the Metathesaurus require separate agreements with the producers of the individual vocabularies.

All the Knowledge Sources are available to licensed UMLS users via the Internet from the UMLS Knowledge Source Server which has a Web interface and an applications program interface (API). UMLS data and program files are available for downloading from the Server and may also be requested on DVD-ROM. A complete description of the Knowledge Sources and their distribution formats can be found in the UMLS Documentation.

For additional information contact:E-mail: custserv@nlm.nih.gov or 1-888-FINDNLM


A complete list of NLM Fact Sheets is available at:
(alphabetical list) http://www.nlm.nih.gov/pubs/factsheets/factsheets.html
(subject list): http://www.nlm.nih.gov/pubs/factsheets/factsubj.html

Or write to:

FACT SHEETS
Office of Communications and Public Liaison
National Library of Medicine
8600 Rockville Pike
Bethesda, Maryland 20894

Phone: (301) 496-6308
Fax: (301) 496-4450
email: publicinfo@nlm.nih.gov

Last updated: 07 May 2004
First published: 01 January 1988
Metadata| Permanence level: Permanent: Stable Content
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