Legal Browser
The Legal Browser is an online vocabulary look-up aid available for use with Legal Index. It is designed to help quickly locate descriptors of possible interest and to show the hierarchy in which descriptors of interest appear. Virtually complete Legal Index records are available, including the scope notes, annotations, entry vocabulary, history notes, allowable qualifiers, etc.

Concept Views

In Descriptors and Supplementary Concept Records (SCRs), after a MeSH record has been retrieved in the Browser, you have the additional option of viewing the “Concept Structure” of the record.

The basic idea is to group synonymous terms into concepts. See Concept Structure in Legal Index. The Standard Concept View provides the minimum concept structure, with terms and scope notes. The Expanded Concept View provides additional concept and term attributes, such as Concept UI, Semantic Type, and Lexical Tag.

Concept Structure in Legal Index

Concept Structure in XML MeSH
A more fine-grained delineation of terms is available in the MeSH data in XML format. Terms in a MeSH record which are strictly synonymous with each other are grouped in a category called a “Concept.” (Not to be confused with Supplementary Concept Records.) See the Concept element in XML MeSH. Each MeSH record consists of one or more Concepts, and each Concept consists in one or more synonymous terms. For example,

Cardiomegaly [Descriptor]
Cardiomegaly [Concept, Preferred]
Cardiomegaly [Term, Preferred]
Enlarged Heart [Term]
Heart Enlargement [Term]
Cardiac Hypertrophy [Concept, Narrower]
Cardiac Hypertrophy [Term, Preferred]
Heart Hypertrophy [Term]
This Descriptor record consists of two Concepts and five terms. Each Concept has a Preferred Term, which is also said to be the name of the Concept. And each record has a Preferred Concept. The name of the record – the term most often used to refer to the Descriptor – is the preferred term of the preferred Concept.

Within each Concept the terms are synonymous with each other. In contrast, the terms in one Concept are not strictly synonymous with terms in another Concept, even in the same record. For example, one concept in a record may be narrower than the Preferred Concept, as in the above example. Also note that the terms in a concept inherit this relationship and so are narrower, for example, than the terms in the other concept. However, all the terms in a record are equivalent for purposes of indexing and searching MEDLINE and so they are still entry terms for the record.

A more complex example, with three Concepts and 12 terms.

AIDS Dementia Complex [Descriptor]
AIDS Dementia Complex [Concept, Preferred]
AIDS Dementia Complex [Term, Preferred]
Acquired-Immune Deficiency Syndrome Dementia Complex [Term]
AIDS-Related Dementia Complex [Term]
HIV Dementia [Term]
Dementia Complex, Acquired Immune Deficiency Syndrome [Term]
Dementia Complex, AIDS-Related [Term]
HIV Encephalopathy [Concept, Narrower]
HIV Encephalopathy [Term, Preferred]
AIDS Encephalopathy [Term]
Encephalopathy, HIV [Term, Preferred]
Encephalopathy, AIDS [Term]
HIV-1-Associated Cognitive Motor Complex [Concept, Narrower]
HIV-1-Associated Cognitive Motor Complex [Term, Preferred]
HIV-1 Cognitive and Motor Complex [Term]
Another example :

Exercise [Descriptor]
Exercise [Concept, Preferred]
Exercise [Term, Preferred]
Exercise, Physical [Term]
Exercise, Aerobic [Concept, Narrower]
Exercise, Aerobic [Term, Preferred]
Aerobic Exercise [Term]
Exercise, Isometric [Concept, Narrower]
Exercise, Isometric [Term, Preferred]
Isometric Exercise [Term]
An example of a chemical (partial record).

Aspirin [Descriptor]
Aspirin [Concept, Preferred]
Aspirin [Term, Preferred]
Acetylsalicylic Acid [Term]
2-(Acetyloxy)benzoic Acid [Term]
Solprin [Concept, Narrower]
Solprin [Term, Preferred]
Ecotrin [Concept, Narrower]
Ecotrin [Term, Preferred]
The Descriptor/Concept/Term structure makes it possible to attach various data elements in MeSH to the appropriate object. For example, thesauri have long distinguished between “broader terms” and “narrower” terms, but it is clear that these are relations between concepts and only derivatively between terms in the concepts. (See the ConceptRelation element.) Similarly, Scope Notes are properly attributed to Concepts, while the Annotation applies to the record level. The Concept structure also provides a precise way to specify strict synonymy since Concepts by definition consist of synonymous terms.

Note that this three-tiered structure is within a given record, not between separate records. This is in contrast to the Legal Index Tree Structures, which is also hierarchical in structure, but the relationships are between different Descriptor records. The XML data include both types of relationships. See “Concepts, Synonyms, and Descriptor Structure” in Introduction to MeSH in XML format.

The MeSH Concept structure is not currently used in MEDLINE indexing or PubMed searching but is used by MeSH analysts in creating and updating the MeSH vocabulary and it supports relationships with other systems such as NLM’s Unified Medical Language System. The Concept structure is also used by The MeSH Translation Maintenance System and has potential use for more advanced technology in information retrieval and other applications. For more information see the following:

1. “Concepts, synonyms, and Descriptor structure” in Introduction to MeSH in XML format.

2. NLM Technical Bulletin article Changes in MeSH Data Structure (includes the example “AIDS Dementia Complex”).

3. The poster presentation Redefining a Thesaurus (includes the example “Exercise”).

4. Book Chapter Relationships in Medical Subject Headings.

5. The section “Concept Structure of MeSH” in the article The MeSH Translation Maintenance System and the related slide presentation The MeSH Translation Database (includes the example “Cardiomegaly”).

6. Articles Tracking Meaning Over Time in the UMLS® Metathesaurus®, and Beyond Synonymy: Exploiting the UMLS Semantics in Mapping Vocabularies, which explicate the role of Concepts in the UMLS Metathesaurus.

Concepts, synonyms, and Descriptor structure

Tagged elements: “human-legible and reasonably clear.”

Instead of short mnemonics, such as ‘DA’ and ‘EV’, the Legal Index uses words.

3.1 Concepts locate synonymy.

Some data elements are new in XML MeSH, independently of the new structure, primarily those elements pertaining to concepts. The concept-centric nature of MeSH is described elsewhere. ³A concept is the common meaning shared by synonymous terms. MeSH and other vocabularies have long used concepts implicitly. With the new MeSH maintenance system introduced with 2000 MeSH, a concept can now be represented simply and precisely by a concept Unique Identifier (<ConceptUI>). Synonymous terms are those terms which share the same <ConceptUI>.

3.2 Descriptors as a class of Concepts

A Descriptor is often broader than a single concept and so may consist of a class of concepts. Concepts, in turn, correspond to a class of terms which are synonymous with each other. Thus MeSH has a three-level structure:

Descriptor

Concept

Term

XML format, with its hierarchical sub-element structure, lends itself to represent these levels. See example below.

3.3 UIs are persistent names for Concepts and other objects

We normally refer to each of these objects by a specific term which names the object, e.g., ‘Heart’, but since this name can be changed, a unchanging numeric code (UI) is assigned to each Descriptor, Concept, and most Terms.* We take advantage of this persistence, using the UI in referring to an object in another record. For example, the “See Related” reference in a record tells the user to consider another Descriptor record. Since the UI is the persistent name of the Descriptor in the SeeRelated element, the UI is included but the Descriptor name is also included.

* Permuted Terms (terms automatically generated by manually entered terms) are on the same level as manually created terms but are importantly different in that the associated <TermUI> element does not identify the term but rather refers to the term from which the Permuted Term was generated.

3.4 Data elements attach to the appropriate object

The Descriptor/Concept/Term structure also makes it possible to attach various data elements in MeSH to the appropriate object. For example, the Scope Note belongs to the concept rather than the Descriptor – a Descriptor may have several different concepts and so several different scope notes. Similarly, thesauri have long distinguished between “broader terms” and “narrower” terms, but it is clear that these are relations between concepts and only derivatively between terms of the respective concepts.