National Library of Medicine
Classification
Professor Yan Ma
National Library of Medicine
Classification Background:
 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 (LCC).
 NLMC follows LCC in both style of
classification and general pattern of
notation.
National Library of Medicine
Classification Background:
 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 numbers.
 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 number.
 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 MeSH.
 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, 1989.
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 easily.
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 (literature).
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 together.
 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 scheme.
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
community.
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 terminology.
 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 conditions.
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.
Summary
 LCC can be a shelf device while DDC can
serve as a retrieval device since OCLC has
bought DDC. DDC is now available Webbased 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.
Summary
 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.