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 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 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 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 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 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 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 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 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 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 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 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 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 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 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 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 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 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 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 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.

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.