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National Library of Medicine Classification


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Title: National Library of Medicine Classification

National Library of Medicine Classification
  • Professor Yan Ma

National Library of Medicine Classification
  • NLM classification is an example of a
    special-subject classification system that was
    expressly designed to be fully compatible with an
    extensive, existing general classification system
  • NLMC follows LCC in both style of classification
    and general pattern of notation.

National Library of Medicine Classification
  • NLMC develops its own classification scheme for
    medicine and related subjects, fitting into LC's
    vacant class W.
  • NLMC develops its own scheme for the pre-clinical
    sciences using LCC's vacant subclasses QS - QZ (Q
    is science).
  • LC also agreed that W and QS-QZ would be
    permanently excluded from LCC.

Basic Rules for NLM Classification
  • 1. The class number assigned to a work is
    determined by the main focus or subject content
    of the work.
  • 2. A work dealing with several subjects that fall
    into different areas of the classification is
    classed by emphasis, or if emphasis is lacking,
    by the first subject treated in the work.

Basic Rules for NLM Classification
  • 3. A work on a particular disease is classed with
    the disease which in turn is classified with the
    organ or region chiefly affected, regardless of
    special emphasis on diet, drug, or other specific
    form of therapy.

Advantages of Using NLM Classification
  • 1. Currency in arrangement of medical material
    and in terminology.
  • 2. Compatibility in terminology with MeSH.
  • 3. Compatibility in notation with LCC.
  • 4. The presence of NLM call numbers in both the
    NLM catalog and its online database, CATLINE.
  • 5. The presence of both NLM class numbers and LCC
    class numbers.

Structure of NLM Classification
  • QS-QZ (8 subclasses)
  • W contains 33 major divisions
  • For example, WS schedule

Notation of NLM Classification
  • 1 or 2 capital letters followed by up to 3 Arabic
  • For example,
  • W1, QS 22.1, WW 100
  • NLMC allows 1-999 integers under each main class
    or subclass, in contrast to the range of 1-9999
    in LCC.

Cutter for NLM Classification
  • NLMC uses Cutter-Sanborn Three-Figure Author
    Table. Cutter by the main entry.
  • Add date to the monographs.

Table in NLM Classification
  • There is only 1 table in NLMC, which is table G
    for geographic subdivisions.
  • Table G is used more widely for monographic
    titles than serial titles.

Table in NLM Classification
  • In the schedule, if there is a note "(Table G)",
    you can add a geographic number to the class
  • W2 is for serials. Table G is used for serials.

Index in NLM Classification
  • The index is very helpful--a very detailed one.
    Major terms are chosen to conform with those in
  • Major terms are in alphabetical order with
    subterms indented under them. Each major term or
    subterm is followed by a class number or a range
    of numbers, including numbers from LCC. See also
    references are also provided under the subterms.

Bibliography Z in NLM Classification
  • The call number for a bibliography in a topic
    listed in NLM schedules begins with the letter Z,
    followed by the class number for the particular
    subject of the bibliography.

Examples of NLMC Numbers
  • The practice of pediatrics in the 1990s by Edwin
    Forman, 1991.
  • WS
  • 21
  • F724p
  • 1991

Examples of NLMC Numbers
  • Children's Memorial Hospital in Chicago by Elaine
    Marieb, 1990.
  • WS
  • 28
  • AA1
  • M334c
  • 1990

Examples of NLMC Numbers
  • Self image in Child Development by Deborah Chang,
  • WS
  • 105.5
  • .S3
  • C454s
  • 1989

Examples of NLMC Numbers
  • Adolescent Medicine by Patrick Murray, 1990.
  • WS
  • 460
  • M983a
  • 1990

Comparison of DDC, LCC, and NLMC
  • Class numbers
  • Notations
  • Cutter numbers
  • Tables DDC tables can be used for all numbers.
    LCC tables are for specific schedules. NLMC only
    has one table.

DDC Merits and Weaknesses
  • Merits
  • 1. It is a practical system. it has been used
    for more than 120 years and it is the most widely
    used classification system in the world.
  • 2. Relative location was invented by Dewey and it
    is now taken for granted.

DDC Merits and Weaknesses
  • Merits
  • 3. The relative index brings together different
    aspects of the same subject scattered in
    different disciplines.
  • 4. The pure notation of Arabic numbers is
    universally recognizable. People from many
    cultures and languages can adapt to the system

DDC Merits and Weaknesses
  • Merits
  • 5. The self-evident numerical sequence
    facilitates filing and shelving.
  • 6. The hierarchical nature of the notation
    expresses the relationship between and among the
    class numbers. This characteristic particularly
    facilitates online searching. The searcher can
    broaden or narrow a search by reducing or adding
    a digit to the class number.

DDC Merits and Weaknesses
  • Merits
  • 7. Use of the decimal system enables infinite
    expansion and subdivision.
  • 8. The mnemonic nature of the notation helps
    library users to navigate within the system.
  • 9. The continuous revision and publication of the
    schedules at regular intervals ensure the
    currency of the scheme.

DDC Merits and Weaknesses
  • Weaknesses
  • 1. The Anglo-American bias is obvious. (900
    geography, 800 literature, 200 religion)
  • 2. Related disciplines are often separated, e.g.,
    300 (social sciences) from 900 (geography and
    history) and 400 (languages) from 800

DDC Merits and Weaknesses
  • Weaknesses
  • 3. The proper placements of certain subjects also
    have been questioned, e.g. library science in
    general works (000s), Psychology as a subdivision
    under philosophy (100s), and sports and amusement
    in the arts (700s)

DDC Merits and Weaknesses
  • Weaknesses
  • 4. In 800, literary works by the same author are
    scattered according to literary form when most
    scholars would prefer to have them grouped
  • 5. The base of 10 limits the hospitality of the
    notational system by restricting the capacity for
    accommodating subjects on the same level of a
    hierarchy to 9 divisions.

DDC Merits and Weaknesses
  • Weaknesses
  • 6. The different rate of growth in various
    disciplines has resulted in a uneven structure.
    Some classes, such as 300 (social sciences), 500
    (natural sciences), and 600 (technology), have
    become overcrowded.

DDC Merits and Weaknesses
  • Weaknesses
  • 7. Even though an existing subject can be
    expanded indefinitely by virtue of the decimal
    system, no new numbers can be inserted between
    coordinate numbers -- e.g., between 610 and 620
    -- even required for the accommodation of new
    subjects. The present method of introducing a
    new subject is to include it as a subdivision
    under an existing subject.

DDC Merits and Weaknesses
  • Weaknesses
  • 8. While capacity for expansion is infinite, it
    also results in lengthy numbers for specific and
    minute subjects. The long numbers have been
    found inconvenient, particularly when the system
    is used as a shelving device.

DDC Merits and Weaknesses
  • Weaknesses
  • 9. Relocations and completely revised (i.e.,
    phoenix) schedules while necessary to keep up
    with knowledge, create practical problems in
    terms of reclassification for libraries using the

LCC Merits and Weaknesses
  • Merits
  • 1. It is a practical system that has proved to be
    satisfactory. "It is a triumph for pragmatism."
  • 2. It is based in the literary warrant of the
    materials in the LC collection, the nature and
    content of which are a reasonable parallel to
    those in academic and research libraries.

LCC Merits and Weaknesses
  • Merits
  • 3. It is largely an enumerative system that
    requires minimal notational synthesis.
  • 4. Each schedule was developed by subject
    specialists rather than by a "generalist" who
    cannot be an expert in every field.

LCC Merits and Weaknesses
  • Merits
  • 5. Its notation is compact and hospitable.
  • 6. There are frequent additions and changes,
    stemming for most part from what is needed in the
    day-to-day cataloging work at LC, and these are
    made readily available to the cataloging

LCC Merits and Weaknesses
  • Merits
  • 7. The need for reclassification of large blocks
    of materials is kept to a minimum because, to
    ensure stability of class numbers, few structural
    changes have been made over the years.

LCC Merits and Weaknesses
  • Weaknesses
  • 1. Its scope notes are inferior to those of DDC.
  • 2. There is much national bias in emphasis and
  • 3. Too few subjects are seen as compounds.
    Multitopical or multielement works for which
    specific provisions have not yet been made cannot
    be classified with precision.

LCC Merits and Weaknesses
  • Weaknesses
  • 4. Alphabetical arrangements are often used in
    place of logical hierarchies.
  • 5. There is no clear and predictable theoretical
    basis for subject analysis.
  • 6. As a result of maintaining stability, parts of
    the classification are obsolete in the sense that
    structure and collocation do not reflect current

LCC Merits and Weaknesses
  • Weaknesses
  • 7. It is expensive to keep an up-to-date working
    collection of schedules, supplements, new
    announcements of changes, and accumulations of
    additions and changes.

  • LCC can be a shelf device while DDC can serve as
    a retrieval device since OCLC has bought DDC. DDC
    is now available Web-based format via CORC.
  • In DDC, you can attach a form device from a
    table, any table can be used.
  • In LCC, you tend to have a screen of numbers.

  • In DDC, Geographic and Historical numbers are
    different, i.e., 910, 930, 999
  • In LCC, Geographic and Historical are combined.
  • LCC numbers are not expressive, but you need to
    look at the indention, finding the meaning of
    those numbers.