http://www.nlm.nih.gov/factsheets.dir/metathesaurus.html (Einblicke ins Internet, 10/1995)

UMLS® Metathesaurus®

The UMLS Metathesaurus is one of four knowledge sources currently under development by the National Library of Medicine as part of the Unified Medical Language System® (UMLS) project. The Metathesaurus supplies information that computer programs can use to interpret user inquiries, to interact with users to refine their questions, to identify which databases contain information relevant to particular inquiries, and to convert the users' terms into the vocabulary used by relevant information sources. The Metathesaurus is intended primarily for use by system developers, but should also be a useful reference tool for database builders, librarians, and other information professionals. The Metathesaurus contains information about biomedical concepts and terms from a number of controlled vocabularies and classifications. It preserves the meanings, hierarchical contexts, and inter-term relationships present in its source vocabularies, adds certain basic information to each concept, and establishes new relationships between terms from different source vocabularies. The scope of the Metathesaurus is determined by the combined scope of its source vocabularies. The Metathesaurus is produced by automated processing of machine-readable versions of its source vocabularies, followed by human review and editing by subject experts.

Content of the 1994 Metathesaurus

Meta-1.4, the 1994 version of the Metathesaurus, includes 190,863 concepts and 371,742 terms (including lexical variants, synonyms, .) from twenty-four different vocabularies. It contains all terms from the 1994 MeSH®, NLM's Medical Subject Headings; DSM-IIIR, the American Psychiatric Association's Diagnostic and Statistical Manual of Mental Disorders, Third edition (revised); the Classification of Nursing Diagnoses; the Home Health Care Classification of Nursing Diagnoses and Interventions; the Nursing Interventions Classification; UMDNS, ECRI's Universal Medical Device Nomenclature System; and AI-Rheum, the NLM Rheumatology expert system. It contains all preferred terms from COSTART, the FDA's Thesaurus of adverse reaction terms; all preferred names of diseases and procedures from ICD-9-CM, the International Classification of Diseases, 9th edition, Clinical Modification; and all procedures from the 1993 SNOMED International. It contains selected terms from other vocabularies, including LCSH, the Library of Congress Subject Headings; CRISP, the USPHS Thesaurus for indexing scientific projects; DxPLAIN, Massachusetts General Hospital's expert diagnostic system; OMIM, Online Mendelian Inheritance in Man; and a set of clinical terms frequently used at three COSTAR sites. Meta-1.4's statistical profile is as follows:

       50,736  MeSH (17,419 preferred terms);
      138,879  MeSH supplementary chemical terms.
       24,794  INSERM French translation of MeSH (Main headings
               and French   Synonym)
       15,256  SNOMED II (8,820 preferred terms)
       27,838  SNOMED International (20,667 preferred terms)
       28,197  ICD-9-CM terms (16,842 preferred terms)
        6,505  CRISP (6,505 preferred terms)
        5,521  LCSH  (5,521 preferred terms)
        2,796  COSTART (1,182 preferred terms)
        1,576  COSTAR  (1,576 preferred terms)
          972  NIC (359 preferred terms)
          777  AI Rheum (687 preferred terms)
          604  Neuronames (604 preferred terms)
          603  DXPlain (603 preferred terms)
          450  DSM 3R (263 preferred terms)
          557  CPT  (210 preferred terms)
          333  HHC (306 preferred terms)
          116  NANDA (108 preferred terms)
          122  ACR (122 preferred terms)
        7,508  UMDNS (4,480 preferred terms)

The Metathesaurus is organized by concept or meaning. Alternate names for the same concept (synonyms, lexical variants, and translations) are linked together. Each Metathesaurus concept has attributes that help to define its meaning, e.g., the semantic type(s) or categories to which it belongs, its position in the hierarchical contexts from various source vocabularies, and, for many concepts, a definition. A number of relationships between different concepts are represented. Some of these relationships are derived from the source vocabularies; others are created during the construction of the Metathesaurus. Most inter-concept relationships in the Metathesaurus link concepts that are similar along some dimension. The Metathesaurus also includes use information, including the names of selected databases in which the concept appears, and, for MeSH terms, information about the qualifiers that have been applied to the terms in MEDLINE®. Information on the co-occurrence of concepts in MEDLINE and in AI-RHEUM is also included.

Distribution Formats

Although sample records are available on IBM PC-compatible and Macintosh diskettes, the complete Meta-1.4 is distributed on CD-ROM only, in combination with the other UMLS Knowledge Sources. Four discs are provided: Two ISO 9660 disc containing the Knowledge Sources in ASCII Relational format data; one with Macintosh HFS browsers; one with the Coachr Meta-94 Browser.

The ISO 9660 CD-ROM files containing all Meta-1.4 data elements are large. The relational files total more than 630 megabytes. These files are distribution formats. Developers can select data elements and choose data representations to meet their own needs. Local hardware and software requirements will be determined by the number and types of elements chosen, by the data representation selected, and by the performance characteristics desired. Any machine equipped to read ISO 9660 CD-ROM discs will be able to access these files.

CD-ROM hardware and software to read ISO 9660 discs is available for the IBM PC, Apple Macintosh, Unix, and many other environments. The Apple Macintosh HFS disc contains an interactive Meta-1.4 HyperCard browser named MetaCard which was developed by Lexical Technology, Inc. Use of this CD-ROM requires a Macintosh SE computer (or later model); 3 megabytes (preferably more) of memory; an Apple (or compatible) SCSI CD-ROM reader, preferably with a 64 kilobyte cache; and the correct SCSI cable(s). Software required includes System 6.0.3 (or later); HyperCard 1.2.5 (or later); and a Start-up document for the CD-ROM reader.

The PC DOS Disc includes the Coach Metathesaurus Browser, and software which installs it. The Coach Browser was developed in NLM's Lister Hill Center. It requires 145 MB of hard disk space, DOS 4,640Kb of RAM, and a color monitor. It may be installed on a Novell network. Other than the Coach Browser, MetaCard, and a Semantic Net Browser, no utilities or applications programs accompany Meta-1.4.

Application Procedures

Those who wish to obtain copies of UMLS products are required to sign a one-year experimental agreement with the NLM. Sample records, documentation, and copies of the experimental agreement, are available from the NLM anonymous ftp file service at nlmpubs.nlm.nih.gov (UMLS files and documents are located in the /nlmpubs/umls directory) or write to:

Betsy L. Humphreys
UMLS Project Officer
National Library of Medicine
8600 Rockville Pike
Bethesda, MD 20894
FAX 301/496-4450

Other Fact Sheets in the UMLS series:

Printed Copies are available from:

Office of Public Information
National Library of Medicine
8600 Rockville Pike
Bethesda, MD 20894

NLM HyperDOC / UMLS Metathesaurus / May 1994