MeSH & Principles of Classification

MeSH & Principles of Classification April 13, 2005

Medical Subject Headings (MeSH) • Thesaurus developed in the 1960s for online use • More detailed than LCSH for medical terminology • Pre-coordinated but not to same extent as LCSH

Vocabulary • Same vocabulary is used for cataloging books and for indexing journals • 19,000 main subject headings • 82 topical subheadings or qualifiers • Each subject heading and qualifier has a scope note and the categories under which it may be used

Vocabulary (cont.) • Does not include form, geographic or language subheadings • Does use publication types as headings • Kinds of study, types of study, and sources of support are specified (“check tags”) • Can limit searching by language, type, medium, location, etc.

Adult Aged Cross-sectional studies Edema/etiology Female Hair/pathology Humans Immunosuppressive agents/*adverse effects *Kidney transplantation Male Middle aged Mucous membrane/pathology Nails/pathology Sebaceous glands/pathology Sirolimus/*adverse effects Skin diseases/*chemically induced Skin diseases, Infectious/etiology Descriptors for:Cutaneous adverse events in renal transplant recipients receiving sirolimus-based therapy (journal article)

Syntax • Some subject headings are inverted • Subject headings may be subdivided, but no more than two elements are permitted • If more than one qualifier is needed, then the subject heading is repeated. Example: Coronary disease / ep [Epidemiology] Coronary disease / me [Metabolism] *Coronary disease / pc [Prevention & Control]

MeSH Thesaurus • Available in three forms online and/or in print: • Tree structure • Alphabetic list • Annotated Alphabetic List • PubMed

Alphabetic List • 1st section: • every subject heading and subdivision in one alphabetical list regardless of hierarchy • notational equivalent(s) • History of the term, including year of adoption, earlier terms • Cross-references

Alphabetic List (cont.) • 2nd section: • Categories and subcategories • Records subcategories in alphabetical order with their notations

Annotated Alphabetic List • Only in print form • Designed for catalogers, indexers, and online searchers • Contains scope notes, check tags, and other information not included in the Alphabetic List

Principles of Classification • Definitions • Uses of classification • Components of classification systems • “Characteristic of division” • Enumerative vs. synthetic schemes

Definitions • Classification: The systematic arrangement of objects or concepts in groups or classes according to their similarities and differences or their relation to a set of criteria. (Olson & Boll, 2001) • In bibliographic classification, like subjects are grouped together and related subjects are near one another

Definitions (cont.) • Class numbers or classification numbers -- symbols used to identify classes (preferably called notation since they can be alphabetic or alphanumeric)

Classification scheme characteristics • Dynamic • Book numbers (a.k.a. Cutter numbers) allow for subarrangement of books within a class • Principles of subarrangement within classes achieved with shelflisting

Uses of Classification • Arrangement of materials on shelves • Arrangement of document surrogates in paper catalogs • Online manipulation of document surrogates (online shelf list) for online browsing

Importance of Browsing • Ranganathan’s principle: Save the time of the user • In open stack libraries, browsing is a significant method of resource discovery • In OPACs which include remote resources, the ability of users to browse an online shelflist increases the likelihood of discovering those remote resources. There is no other way at present to browse remote resources. • The library’s efforts to fully classify a collection results in time savings for users and staff.

Components of a Classification Scheme • verbal description of things and concepts • arrangement into a classed/logical order that is meaningful and convenient • notation alongside each verbal description; together these form schedules • references to guide user to other aspects of topics or related topics

Components of a Classification Scheme (cont.) • alphabetical index of terms used in the schedules with synonyms • instructions for use • mechanisms for revision

Characteristic of division • Groups of abstract concepts, objects, or activities are divided into smaller groups • The criterion for division is called the “characteristic of division”

Types of Characteristics of Division (cont.) • Genus to species (or group to member) Primates to Apes • Whole to parts Nervous system to Spinal cord • Continuous process Textiles, Carding, Spinning, Weaving, Finishing

Types of Characteristics of Division (cont.) • Increasing complexity Music for duets, for trios, for quartets • Chronological (history of a country) Czechoslovakia, 1918-1939, 1939-1945, 1945-1968 • Spatial: Continent to Country Europe to Czech Republic

Characteristics of Division (cont.) • Division continues until no other divisions can be made • Creates a hierarchy • Overlapping hierarchies may exist as there may be more than one way of dividing a topic

Enumerative Classification Schemes • Every topic that can be classified is enumerated in the scheme • Topics not enumerated separately must be classed with a broader topic • Narrow compound topics can be accomodated by narrowing the class

Linearity • Linearity: documents can only be shelved by one characteristic • Only major aspects of a work are considered in classification • Compound topics present a problem

Solutions to compound topics • Rules: • Classify by emphasis of the work • Classify by one criterion when two apply • Classify by the first class in the schedules • These rules can be arbitrary and are of no use to browsers

Synthetic Classification • Combine notations for different concepts to create compound notations • Faceted classification is one type of synthetic classification • Ranganathan’s colon classification – five facets • Read more about it in Chapter 7, SAOC!

MeSH & Principles of Classification