edited by Birger Hjørland and Claudio Gnoli


Nippon Decimal Classification (NDC)


Table of contents:
1. Introduction
2. Brief history
    2.1 Early editions (1929-1949)
    2.2 JLA editions (1950-1986)
    2.3 Present day (1986-)
3. Classification schedules
    3.1 Main classes
    3.2 Division, section and subsection
    3.3 Auxiliary tables: 3.3.1 General division tables; 3.3.2 Proper division tables
    3.4 Alternative locations
    3.5 Disused entry
    3.6 Relative Index
4. Notation system
    4.1 Irregular hierarchical structure
    4.2 Number building
    4.3 Classification code
5. Electronic versions
    5.1 MRDF
    5.2 NDC-LD (Linked Data) and NDC Data
6. Conclusion

The Nippon Decimal Classification (NDC: 日本十進分類法) is a standard library classification in Japan and is adopted by almost all kinds of libraries. The NDC was originally developed by Kiyoshi Mori (1906-1990), and it has been maintained and revised by the Committee of Classification of the Japan Library Association since 1948. Following a brief history of the NDC, describes characteristics of schedules, notation and classification codes. Two electronic versions of the NDC, i.e., Machine Readable Data File (MRDF) and Linked Data format are explained.

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1. Introduction

The Nippon Decimal Classification (NDC: 日本十進分類法 in Japanese; pronounced as “Nihon-Jisshin-Bunruiho”) is regarded as a standard → library classification system in Japan. The first edition was developed in 1929 by Kiyoshi Mori (1906-1990), and the latest is the “Newly 10th edition” of 2014 revised by the Committee of Classification of the Japan Library Association (JLA) (Mori and JLA 2014).

Before the advent of NDC or sometime after it, almost all of libraries in Japan had used their own classifications. When the NDC became standardized after World War II, the number of users began to increase. Section 2 introduces a brief history of the NDC (and other classifications used in Japan).

The NDC is an enumerative classification with decimal → notation, but the system allows number buildings in places using auxiliary tables for subdivision. The notation possesses mnemonic qualities about forms, geographic treatments, languages, periods and so on. As a decimal notation system the NDC is akin to the Dewey Decimal Classification (DDC), but the order of main classes stemmed from Cutter's Expansive Classification (EC). The NDC was a product of the deviser’s careful study of foreign classification at the time. Section 3 explains the structure of the NDC and its divisions. Section 4 explains its notation and classification codes.

Today, the NDC have two kinds of electronic version. One is the Machine-Readable Data File (MRDF) format and the other is the Linked Data format (NDC-LD and NDC Data) for experimental use. Section 5 gives an outline of these two versions.

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2. Brief history

The history of the NDC and its usage at that time will be explained in three periods (Fujikura 2018).

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2.1 Early editions (1929-1949)

In August 1929 Kiyoshi Mori published the first edition of The Nippon Decimal Classification (Mori 1929) with the help of the Mamiya-shoten (F. Mamiya & Company: 間宮商店) where he worked as a staff member at the time. It based on the draft in 1928 (Mori 1928a; 1928b). Mori revised the NDC in cooperation with experts on each subject. During about 15 years from the 1st edition, the NDC became the 5th edition (1942).

The statistics about users of those editions only appeared in introduction to each edition. The NDC2 shows 25 libraries adopt the NDC (Mori 1931), and "over 100 and more" in the NDC3 (Mori 1935). But what is written in the NDC5: “Today, we think perhaps the numbers of libraries using the NDC for organization of books are more than 1,000” (Mori 1942) is a little suspicious.

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2.2 JLA editions (1950-1986)

After World War II, the Japanese library world reconstructed under advices by CIE (Civil Information and Educational Section) of the GHQ/SCAP. From 1947 to 1948, CIE discussed with Japanese librarians about standardizing library classification and reached two decisions. (1) CIE’s Library Officer Paul J. Burnette decided to adopt outline of the NDC to The Guideline to School Libraries (Ministry of Education 1948). (2) CIE’s Special Consultant Robert B. Downs recommended the use of the NDC for the classification of Japanese books in the National Diet Library on his report (Downs 1948). As a result, the NDC has acquired the status of a standard classification in Japan. In responding to those discussions, the Japan Library Association (JLA) set up the Committee of Classification in 1948 and Shuko Kato (1895-1981), the president of the National Library became the first chairman. Mori too became a member of the committee, and often advised the revision of the NDC.

The newly 6th edition of the NDC was published by the JLA in 1950 (Mori and JLA 1950). The word "newly" capped for revised edition by the JLA, and it continues to today. The NDC was revised to the 7th (1961) and 8th (1978).

From the 1950s to the 1970s, Japanese libraries (public-, school- and academic libraries) had increased in number, and many of them adopted the NDC (containing old editions).

According to surveys from the JLA in 1964, 92% public libraries, 68% university libraries, and 89% college libraries adopted the NDC (Mori 1966), and in 1972, 95% public libraries and 83% university libraries, and 98% college libraries adopted the NDC (Mori 1982).

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2.3 Present day (1986-)

In 1986, Mori retired from the committee at the age of 80, and he died in 1990. At the time, JLA had begun to revise the 9th edition (1995). And in 2014, the latest 10th edition was published.

Presently, almost all Japanese library use the NDC. In public libraries 99.4% use all books in any languages. In university, 92.1% use the NDC, because some libraries using the DDC or other classification systems for foreign books (Omagari 2008).

School libraries have no complete survey of libraries, but a survey on sample libraries shows using the NDC in most schools’ libraries (Japan School Library Association 2008). This survey shows the usage of the NDC in primary schools reaching 89.7%, in junior high schools 92.7% and high schools 99.3%.

There are no statistical surveys for special libraries, but directories show many libraries using the NDC (Japan Special Libraries Association 2018). Libraries not using the NDC uses (1) their own classifications (2) DDC (especially for holding many foreign books) (3) UDC (especially at special libraries or collections), and (4) specialized classification system for specific subjects or collections (e.g. medical library).

The NDC is given to students at a lecture on classification at most universities’ course for librarians in Japan.

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3. Classification schedules

The NDC uses three-digit Arabic numerals to classify subjects, and for specific subdivisions a decimal point is inserted between the third and the fourth digits as the DDC does.

The first division level (classes into ten) is called class or main class, the second level (hundred) is division, and the third (thousand) is section. A subdivision following a decimal point is called subsection.

Class0General Works
Division01   Library and information science
Section014      Technical processes in libraries
Subsection014.4         Indexing: Classification, Subject headings, Subject analysis
014.45            Standard classification

The NDC schedules and tables are expressed in Japanese, but captions of main classes, divisions and sections are accompanied by English ones (or other languages for the name of persons or nations).

In the example above, captions of 0 to 014 are quoted from the original NDC 10th edition (abbreviated to “NDC10”), and those of 014.4 to .45 are translated by the author of this article.

In the 1920s the original editor Mori studied classification schemes used abroad, such as the EC, the DDC (Mori used the 12th edition), the Library of Congress Classification, and the Universal Classification (by Du Dingyou in China, 1922). He concluded that the order of main classes of the EC was the best. He also valued the device of mnemonics, auxiliary tables and relative index recognized in the DDC. Thus, the idea occurred to him that arrangement of subjects based on Cutter’s EC with a decimal notation system would be possible.

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3.1 Main Classes

Below is a comparison of main classes among the DDC (Dewey 1927), the EC (Cutter 1891-1893) and the NDC.

The first ten main classes of the NDC are derived from those of Cutter’s EC. The class 0 means “General works” but contains some interdisciplinary subjects. In the first draft of 1928 Mori placed literature at class 8 and language at 9, but he inverted the order in the NDC 1st edition as in the EC. The order of main classes of the NDC has been kept unchanged through all editions, but class names were sometimes changed either in Japanese terms or in English ones.

DDC12 (1927)

000 General Works
100 Philosophy
200 Religion
300 Sociology
400 Philology
500 Pure Science
600 Useful Arts
700 Fine Arts
800 Literature
900 History

EC (1891)

A   General works
B-D Philosophy/Religions
E-G History/Geography
H-K Social sciences
L-Q Natural sciences
R-U Arts
V-W Music/Graphic
X   Language
Y   Literature
Z   Book arts

NDC1 (1929)

0 General Works
1 Spiritual sciences
2 Historical sciences
3 Social sciences
4 Natural science
5 Technology
6 Productive arts
7 Fine arts
8 Science of Language
9 Literature

NDC10 (2014)

0 General works
1 Philosophy
2 History
3 Social sciences
4 Natural sciences
5 Technology
6 Industry
7 The arts
8 Language
9 Literature

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3.2 Division, section and subsection

The order of classes in the first division is similar to that of the EC, but subclasses are arranged by giving priority to matters in Japan (e.g., Japan is located first in the fields of history, geography and language). In addition, subclasses are divided according to conditions of Japanese society, custom and culture. For example, Buddhism in the DDC is located at 294 as a section, while in the case of EC it is not found even in the most detailed “Sixth classification” table (but one can find Buddhism under Bz “local religion” by using the index). The NDC locates Buddhism at 180 in its division.

The second outline of NDC10 follows (English class names are used as they stand in the main NDC10 schedule).

000 General works
010    Libraries. Library and information sciences
020    Books. Bibliography
030    General encyclopedias
040    General collected essays
050    General serial publications
060    General societies
070    Journalism. Newspapers
080    General collections
090    Rare books. Local collections. Special collections

100 Philosophy
110    Special treatises on philosophy
120    Oriental thought
130    Western philosophy
140    Psychology
150    Ethics. Morals
160 Religion
170    Shinto
180    Buddhism
190    Christianity

200 General history
210    General history of Japan
220    General history of Asia
230    General history of Europe
240    General history of Africa
250    General history of North America
260    General history of South America
270    General history of Oceania. General history of Polar regions
280    General biography
290    General geography. Description and travel

300 Social sciences
310    Political science
320    Law
330    Economics
340    Public finance
350    Statistics
360    Society
370    Education
380    Customs,folklore and ethnology
390    National defence. Military science

400 Natural sciences
410    Mathematics
420    Physics
430    Chemistry
440    Astronomy. Space sciences
450    Earth sciences
460    Biology
470    Botany
480    Zoology
490 Medical sciences

500 Technology. Engineering
510    Construction. Civil engineering
520    Architecture. Building
530    Mechanical engineering
540    Electrical engineering
550    Maritime engineering
560    Metal and mining engineering
570    Chemical technology
580    Manufactures
590 Domestic arts and sciences

600 Industry and commerce
610    Agriculture
620    Horticulture
630    Sericulture. Silk industry
640    Animal husbandry
650    Forestry
660    Fishing industry. Fisheries
670    Commerce
680    Transportation services
690    Communication services

700 The arts. Fine arts
710    Sculpture. Plastic arts
720    Painting. Pictorial arts
730    Engraving
740    Photography and photographs
750    Industrial arts
760    Music
770    Theater
780 Sports and physical training
790 Accomplishments and amusements

800 Language
810    Japanese
820    Chinese
830    English
840    German
850    French
860    Spanish
870    Italian
880    Russian
890    Other languages

900 Literature
910    Japanese literature
920    Chinese literature
930    English and American literature
940    German literature
950    French literature
960    Spanish literature
970    Italian literature
980    Russian literature
990    Literatures of other languages

Some class numbers have mnemonic qualities. For example, the number 1 often stands for Japan such as: 210 History of Japan; 910 Japanese literature; 051 Japanese serial publications; and 721 Japanese painting.

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3.3 Auxiliary tables

Like many other book classification systems, the NDC has some auxiliary tables for subdivisions. In the NDC10, they are divided into two groups: (1) general division tables and (2) proper division tables.

Those subdivision numbers are added after any class number or instructed. If the last digit of the class number to which a subdivision is to be made ends with 0 (at main class or division), remove the 0 and then add the subdivision number.

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3.3.1 General division tables

General divisions comprise 4 tables: form division (Table I); geographic division (Table I-a); sea division (Table II); and language division (Table III).

The form division needs to add -0 and something after any class number.

The geographic division needs to add after a form division number -02 historic/geographic treatment” (or add it directly when instructed). For example:

143 Developmental psychology + -033 Dictionary. Glossary
= 143.033 Dictionary of developmental psychology

140 Psychology → (remove 0) → 14 Psychology + -033 Dictionary. Glossary
= 140.33 Dictionary of psychology

013.1 Librarian + -02 (from form division number) + -1 Japan
= 013.1021 Librarians in Japan

016.2 Public Library (*add geographic division) + -136 Tokyo
= 016.2136 Public libraries in Tokyo

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3.3.2 Proper division tables

Proper divisions comprise 10 tables: e.g., subdivisions for religious topics of Buddhism sects (under 188) as Table 2; Subdivision of individual languages (under 810/890) as Table 9; and Subdivision of individual literatures (under 910/990) as Table 10.

The usage of these tables is simple as a subdivision number has only to be added to the end of the class number. For example:

188.8 Zen + -5 Temple, monk, commandment (from Table 2)
= 188.85 Temple of Zen (or Monks of Zen)

800 Language + -1 Japanese (from language division) + -3 Dictionary (from Table 9)
= 813 Japanese dictionary

800 Language + -493 Dutch + -3 Dictionary
= 849.33 Dutch dictionary

900 Literature + -1 Japanese (from language division) + -1 Poetry (from Table 10)
= 911 Japanese poetry
NB: 911 has some more subdivisions, e.g., 911.3 Haiku; 911.33 Haiku in Genroku period (1688-1704).

900 Literature + -493 Dutch + -1 Poetry
= 949.31 Dutch poetry

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3.4 Alternative locations

Requests made mainly by special libraries or collections caused the preparation of alternative locations as to some classes and subclasses. This kind of locations is indicated by using the symbols [ ] and →.

143 Developmental psychology
    .1 Gender psychology
   [.2] Infant psychology →376.11
   [.3] Child psychology →371.45
   [.4] Adolescent psychology →371.47
    .5  Female psychology

In the example above, the entry “Child psychology” is an alternative location, and the class number is given as [.3] (143.3) and referred as “→371.45” (it means “see 371.45”).

In 371 below, “Child psychology” is located at 371.45, and there is an asterisked scope note on the use of the alternative (and 371.47 is also same as .45).

Also, in the example, 371.45 refers to 367.6 (“→:367.6”, it means “see also 367.6”), and 371.44 is again an alternative location (same example as 143.2).

371 Theory of education
   .4 Educational psychology. Educational environment
  [.44] Infant psychology →376.11
   .45 Child psychology. Child research →: 367.6
              *Alternative into 143.3
   .47 Adolescent psychology. Adolescent research →: 367.6
              *Alternative into 143.4

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3.5 Disused entry

As a result of the revision procedure, it is decided that some class numbers and/or names should be deleted or relocated. These unusable numbers or names are given in brackets in the revised edition and will be deleted in the next one. Examples of disused entries in the NDC10 are as below:

(017.6 College library → 017.8)
(547.458 Telex)

The symbol → in the first example means "see" reference, so it refers the user to the new class number (017.8 College library. Technical college library). When both a class number and a name are deleted altogether as in the second example, it is advised to use next generic class, i.e., a book on Telex should be classified at 547.45 Telegram.

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3.6 Relative Index

Schedules of the NDC have been supplemented with a subject index from its inception. The original editor Mori recognized the necessity and effectiveness of subject index, though other most classifications employed in Japan at that time did not have indexes. Even the first draft of the NDC published as a journal article (see section 2.1) had indexes comprising 3,050 terms and including subject index of over 2,600 terms and indexes of geographic names, language and so on. The 1st edition of the NDC had indexes comprising 5,500 terms and including a subject index of about 5,000 terms. Until the 5th edition, the index was called “Relative Subject Index” (相関件名索引 in Japanese), and indexes for geographic names, languages etc. were separated as mentioned above. Indexes of foreign geographic names and languages were given in English, so they were useful for Japanese librarians at that time.

When the revision work with the NDC6 was handed over the JLA, the index was renamed “Relative Index” (相関索引 in Japanese). The number of the index terms continued to increase: there were about 21,800 terms in the NDC8; about 29,500 in the NDC9; and about 33,000 in the NDC10. The index terms were sorted by Romanization before the NDC7, but now sorted by the Japanese syllabary.

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4. Notation system

The NDC uses three-digit Arabic numerals for class/subclasses and decimal point (period) for subsections. No other symbols are used. The decimal notation reflects the hierarchical structure.

4.1 Irregular hierarchical structure

As this example shows, class numbers usually reflect the hierarchical structure.

6 Industry
67    Commerce
675        Marketing
675.1          Merchandise. Merchandising
675.18             Commodity packaging. Label

However, an irregular case occurs owing to → the number of subdivisions, which does not fit decimal system. If there are fewer or more subdivisions than 10, notation cannot reflect the hierarchical structure faithfully and vice versa.

Next example shows that 012.2 and 012.28/.29 are arrayed on the equal level, and that 012.3 and 012.4/.7 form a single hierarchal structure (012.4 means “design” of “stack room”).

012 Library buildings
.1     Plan of buildings: Substructure planning, location, site
.2     Materials and structure
.28   Repair or reconstruction
.29   Maintenance. Protection. Fire-prevention. Watertight
.3     Design and draft
.4       Stack room. Bookshelf
.5       Rooms for users: Reading room, children's room, catalogue room
.6       Auditorium. Meeting room. Exhibition room. Audio visual room
.7       Office. Other rooms for management
.8     Library equipment: Sanitary facilities, mechanical equipment, electric equipment

In another case, when there are many subdivisions, a kind of skip-numbering procedure is adopted by using the symbol [ ] in which an unusable number is given, and subdivisions are enumerated with two-digit notation respectively. Next example means that 619 Agricultural technology has many subsections and it is difficult to group 619.11/.18 into the same one category. Therefore, 619.1 is skipped as [.1], and 619.11/.18 are enumerated as direct subdivisions under 619.

619 Agricultural technology
.11      Agricultural water. Drainage
.12      Fuel. Power
.15      Operation
.16      Microzyme: Mold, yeast, bacterium
.18      Agricultural manufacturing machine: Rice mill, barley cleaning machine, grinding mill, noodle making machine
.2     Grain cleaning. Cataclasis

Sometimes the 9th subdivision may be used as “others”. Next example shows that 880 Russian (language) is divided in accordance with subdivision of individual languages as 881/888. The 9th subdivision of 889 is used for “other” Slavic languages collectively and divided according to individual languages, e.g., 889.1 Bulgarian.

880 Russian
881/888 (linguistic topics of Russian: vocabularies, grammar, readers, etc.)
889 Other Slavic languages
.1    Bulgarian. Macedonian
.2    Serbian. Croatian. Bosnian. Montenegrin
.3    Slovene ...

It was the NDC9 that employed the device of so-called “centered entry” using the symbol < >. As showed in next example, the purpose of the device is to insert a range of different applications of characteristics into regular hierarchical structure.

311 Political theory and thought
.1    Political philosophy
.2    History of political theory and thought
<.3/.9    Specific kinds of political thought>
.3    Ultranationalism. Nationalism. Racialism
.4    Conservatism
.5    Absolutism ...

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4.2 Number building

The method of number building in the NDC is limited in its number and relatively simple. Instructions are given by as scope notes.

  1. Using auxiliary tables (see section 3.3)
  2. Simple addition of a two-digit subclass number (100 division; see section 3.2) to specify a kind of something as below:
    018 Special libraries (*add to division for kinds of library) + 49 Medical sciences
    = 018.49 Medical library

  3. Two kinds of geographic divisions for use in interaction between two countries.

    Next example instructs that 678.2 + -1 “Japan” forms 678.21 “Trade history of Japan”, and that addition of 0 + -53 “United States” results in 678.21053 “Japan-US trade”.

    678.2 Trade history
             * add geographic division
             * for bilateral trade, add a zero after geographic division, and add geographic division of a partner country e.g., 678.21053 Japan-US trade

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4.3 Classification code

Regarding early editions of the NDC, Mori did not prepare any code for the NDC users. Shuko Kato (see also section 2.2) made a draft of a classification code for the NDC (Kato 1931). The draft was based on his translation of W.S. Merrill’s Code for classifiers into Japanese (Merrill 1928) and was welcomed gladly. In 1950 the NDC6 included its classification code for the first time, which was largely based on Kato’s work. It can be said that the NDC’s classification code stemmed from the works of Kato, Merrill and Dewey, the last of whom was the origin of modern library classification and its code. The following are main code rules of the NDC10 (Kanise 2015; Kobayashi 2017):

  1. Classification by aspects
    The NDC is an aspect classification from the viewpoints of various → disciplines. Accordingly, a work should be classified under the subject aspect of a discipline. If a work is treated from more than two aspects, it should be classified under the central or most basic subject.
  2. Subject and form
    A work should be classified first by subject and next by its form using auxiliary tables (see section 2.3). Exceptions are class 0 (general works) and class 9 (literature). In class 0, a work should be classified first by its form (e.g., encyclopedias or serials). In class 9, a work should be classified first by language and next by its literary form (see section 3.3.2).
  3. Original and related works
    Works that relate to the original, such as translations or remakes, should be classified at the same place that the original has been placed.
  4. Polytopical works
    A work consisting of several topics independently should be classified under the subject of the main or central topic. But when the work has no main or central topic, the decision is made according to the number of topics. If the work has 2 or 3 topics, it should be classified under the subject of the first topic. If the work has 4 or more topics, it should be classified under the upper class.
  5. Relations between two subjects
    Several codes are prepared for the treatment of those subjects which result from relations between two independent subjects. The above subjects to be treated are usually called “complex subjects”, and relations between two independent subjects, such as Influence, Causation, Comparison, etc., are called “phase relations”. The NDC employs the passive voice. For example, a work studying the relation between “an action” and “action applied” should be classified under the subject of “action applied”.
  6. New subjects or topics
    A work that treats a new subject or topic which is not established should be located at the close subject or under the superordinate one.

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5. Electronic versions

At present, two kinds of electronic version of the NDC exist. One is the MRDF (Machine Readable Data File), which can be alternative to printed version. The other is the Linked Data format which can be used for web services or database systems.

5.1 MRDF

In 1989 the MRDF of the NDC 8th edition (MRDF NDC8; or MRDF8) was published. The MRDF was comprised of tagged main schedules and tagged relative index, both of which were simple structure. The MRDF9 (1996) took the same format as the MRDF8.

After the NDC10 published, the JLA committee discussed the format of the new MRDF. They discussed a small change of the format and a relative index which had omitted terms on print version (e.g., different characters, rare terms and old concepts), and the MRDF10 was published in 2020.

Though the MRDFs are not major files, they are sometimes used in OPACs of libraries, or for experiments by library and information science researchers. The MRDF9 was used also as basic data for the revision of the 10th edition.

An example of the MRDF10 tags and descriptions follows.

00017200A01000020Libraries.Library and information sciences

An example of schedule descriptions in the same class of the NDC10 follows.

010  図書館.図書館情報学  Libraries. Library and information sciences
  →: 007 ; 020
   .1   図書館論.図書館の自由
  [.13]     図書館職員の倫理 →013.1

In the above examples, the meanings of each tag and code are as follows.

00017100code number
Aflag of table/index
010class number
010.1 class number
010.13class number
00010name of entry
00020name in English
00040scope note
00060see also reference
01010alternative name
01060alternative (see) reference

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5.2 NDC-LD (Linked Data) and NDC Data

In 2015, the National Diet Library and the JLA implemented a cooperative research project to create Linked Data for the NDC (Nakai et al. 2016).

This pilot project contained: (1) conversion from MRDF8 and 9 to a Linked Data format (2) development of hierarchical structure model for NDC classes, metadata schema for the NDC semantics and a label for contexts. The project named the "NDC-LD" ended in August 2016.

Then the JLA decided on a simplified model of the NDC-LD, and open to public use named the “NDC Data (ndc8 and 9)” in March 2019. The NDC Data is licensed under Creative Commons “CC-BY”. The NDC Data can be downloaded as RDF/XML, Turtle, JSON and original format (https://www.jla.or.jp/committees/bunrui//tabid/789/Default.aspx).

As a user example, the developer company Calil is providing an API and open source data converted from the NDC Data (https://ndc.dev/). The Japan Search (beta version) as a digital archives portal by National Diet Library adopted the NDC-LD based NDC9 (https://jpsearch.go.jp/).

An example follows of RDF/XML format from the NDC data (ndc9).

    <skos:Concept rdf:about="http://jla.or.jp/data/ndc9#010">
       <skos:narrower rdf:resource="http://jla.or.jp/data/ndc9#016"/>
       <skos:narrower rdf:resource="http://jla.or.jp/data/ndc9#016.9"/>
       <skos:relatedMatch rdf:resource="http://id.ndl.go.jp/auth/ndlsh/00573404"/>
       <skos:relatedMatch rdf:resource="http://id.ndl.go.jp/auth/ndlsh/00617035"/>
       <skos:relatedMatch rdf:resource="http://id.ndl.go.jp/auth/ndlsh/00831135"/>
       <ndcv:indexedTerm rdf:parseType="Resource">
       <skos:relatedMatch rdf:resource="http://id.ndl.go.jp/auth/ndlsh/00573385"/>
       <skos:related rdf:resource="http://jla.or.jp/data/ndc9#007"/>
       <skos:relatedMatch rdf:resource="http://id.ndl.go.jp/auth/ndlsh/00573401"/>
       <skos:relatedMatch rdf:resource="http://id.ndl.go.jp/auth/ndlsh/001209171"/>
       <skos:narrower rdf:resource="http://jla.or.jp/data/ndc9#019"/>
       <skos:inScheme rdf:resource="http://jla.or.jp/data/ndc9#"/>
       <dcterms:isVersionOf rdf:resource="http://jla.or.jp/data/ndc#010"/>
       <ndcv:indexedTerm rdf:parseType="Resource">
       <skos:prefLabel xml:lang="en">Libraries.Library and information sciences</skos:prefLabel>
       <skos:narrower rdf:resource="http://jla.or.jp/data/ndc9#013"/>
       <skos:narrower rdf:resource="http://jla.or.jp/data/ndc9#011"/>
       <skos:narrower rdf:resource="http://jla.or.jp/data/ndc9#010.6"/>
       <skos:relatedMatch rdf:resource="http://id.ndl.go.jp/auth/ndlsh/00573391"/>
       <ndcv:indexedTerm rdf:parseType="Resource">
       <dcndl:transcription>トショカン ジョウホウガク</dcndl:transcription>
       <skos:narrower rdf:resource="http://jla.or.jp/data/ndc9#014"/>
       <skos:narrower rdf:resource="http://jla.or.jp/data/ndc9#012"/>
       <skos:prefLabel xml:lang="ja">図書館.図書館学</skos:prefLabel>
       <rdf:type rdf:resource="http://jla.or.jp/vocab/ndcvocab#Section"/>
       <skos:narrower rdf:resource="http://jla.or.jp/data/ndc9#010.7"/>
       <skos:narrower rdf:resource="http://jla.or.jp/data/ndc9#015"/>
       <skos:narrower rdf:resource="http://jla.or.jp/data/ndc9#010.21"/>
       <skos:broader rdf:resource="http://jla.or.jp/data/ndc9#01"/>
       <skos:narrower rdf:resource="http://jla.or.jp/data/ndc9#010.1"/>
       <skos:related rdf:resource="http://jla.or.jp/data/ndc9#020"/>

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6. Conclusion

The growth of the NDC has kept in step with the expansion of Japanese library world. During the period while revision was carried out by Mori with the help of his supporters, the NDC came to be used by many libraries. And after the war the NDC became a standard classification system under the aegis of the JLA. However, as the number of libraries using the NDC increased, the pressure that a drastic revision was needed increased.

In the late of the 20th Century, the DDC and some other classifications started to adopt → facet analysis and faceted notations. But NDC remains a simple enumerative system. Also, the NDC10 is still faced with the problem of its crampedness, old-fashioned subdivisions and strange categories. For this reason, the system suffers from imbalance and is unable to cope with new social problems or events.

As a standard library classification in Japan, the NDC will cope with the problems mentioned above. The NDC must be forced to carry out a bold revision, including the way of “phoenix schedules” which the DDC adopted. The Committee of Classification of the JLA has already started discussion about the coming 11th edition.

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I thank Dr. Keiichi Kawamura for encouraging me to write this article and introducing me to the editors. I received the cooperation of the Committee of Classification of the Japan Library Association (JLA) to write the article. The opinions expressed in the article do not necessarily reflect the views of the committee or of the JLA.

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