Editing Universal Decimal Classification

[[File:Étiquettes de classement de la CDU - Bibliothèque de la maison Léon Losseau.jpg|thumb|right|Universal decimal classification used at the library of the [[maison Losseau]].]]
{{short description|Bibliographic and library classification system}}
The '''Universal Decimal Classification''' ('''UDC''') is a [[bibliographic]] and [[library classification]] representing the systematic arrangement of all branches of [[human knowledge]] organized as a coherent system in which knowledge fields are related and inter-linked.<ref name="UDC Fact Sheet">{{cite web |title= UDC Fact Sheet |url=http://www.udcc.org/index.php/site/page?view=factsheet |website=UDC Consortium website |access-date=28 October 2018 |language=en }}</ref><ref>{{cite book |last=McIlwaine |first=I. C. |author-link=Ia McIlwaine |title=Universal Decimal Classification: a guide to its use |edition=Revised |location=The Hague |publisher=UDC Consortium |year=2007}}</ref><ref>{{Cite encyclopedia|doi=10.1081/E-ELIS3-120043532 |title=Universal Decimal Classification (UDC) |year=2009 |encyclopedia=Encyclopedia of Library and Information Sciences |edition=Third | pages=5432–5439 | last1 = McIlwaine | first1 = I. C. | isbn=978-0-8493-9712-7 }}</ref><ref>{{cite book |doi=10.29085/9781783302383.019 |chapter=Universal Decimal Classification 1: General properties and basic number building |title=Essential Classification |date=2017 |pages=241–264 |isbn=9781783302383 }}</ref><ref>{{cite book |doi=10.29085/9781783302383.020 |chapter=Universal Decimal Classification 2: Auxiliary tables |title=Essential Classification |date=2017 |pages=265–298 |isbn=9781783302383 }}</ref> The UDC is an analytico-synthetic and [[faceted classification]] system featuring detailed [[controlled vocabulary|vocabulary]] and syntax that enables powerful [[Subject indexing|content indexing]] and [[information retrieval]] in large collections.<ref name="UDC History">[http://www.udcc.org/index.php/site/page?view=about_history UDC History], "About UDC" - UDC Consortium website</ref><ref>{{cite journal|doi=10.1002/(SICI)1097-4571(199704)48:4<331::AID-ASI6>3.0.CO;2-X | volume=48 | issue=4 | title=The Universal Decimal Classification: Some factors concerning its origins, development, and influence | year=1997 | journal=Journal of the American Society for Information Science | pages=331–339 | last1 = McIlwaine | first1 = I. C. }}</ref> Since 1991, the UDC has been owned and managed by the UDC Consortium,<ref>[http://www.udcc.org/index.php/site/page?view=about_udcc UDC Consortium], UDC Consortium website</ref> a non-profit international association of publishers with headquarters in [[The Hague]], Netherlands.

Unlike other library classification schemes that started their life as national systems, the UDC was conceived and maintained as an international scheme. Its translation into other languages started at the beginning of the 20th century and has since been published in various printed editions in over 40 languages.<ref>[http://www.udcc.org/index.php/site/page?view=editions UDC Editions], UDC Consortium website</ref><ref>{{cite journal |last1=Slavic |first1=A. |title=UDC Translations: a 2004 Survey Report and Bibliography |journal=Extensions & Corrections to the UDC |date=November 2004 |volume=26 |issue=2004 |pages=58–80 |language=en|hdl=10150/106363 }}</ref> UDC Summary, an abridged Web version of the scheme, is available in over 50 languages.<ref name="UDCS" /> The classification has been modified and extended over the years to cope with increasing output in all areas of human knowledge, and is still under continuous review to take account of new developments.<ref>[http://www.udcc.org/index.php/site/page?view=major_revisions Major Revisions of the UDC 1993-2013], UDC Consortium website</ref><ref>{{cite journal |last1=Slavic, A. |last2=Cordeiro, M. I. |last3=Riesthuis, G. |title=Maintenance of the Universal Decimal Classification: overview of the past and preparations for the future |journal=International Cataloguing and Bibliographic Control |date=June 2008 |volume=37 |issue=2 |pages=23–29 |language=en|hdl=10150/105220 }}</ref>

Albeit originally designed as an indexing and retrieval system, due to its logical structure and scalability, UDC has become one of the most widely used knowledge organization systems in libraries, where it is used for either shelf arrangement, content indexing or both.<ref>{{cite journal |last1=Slavic |first1=A. |title=UDC implementation: from library shelves to a structured indexing language |journal=International Cataloguing and Bibliographic Control |date=2004 |volume=33.3 |issue=2004 |pages=60–65 |language=en|hdl=10150/105685 }}</ref> UDC codes can describe any type of document or object to any desired level of detail. These can include textual [[Document|documents]] and other media such as [[film]]s, [[video]] and [[sound]] recordings, [[illustration]]s, [[map]]s as well as [[realia (library science)|realia]] such as [[museum]] objects.

== History ==
[[File:La classification Décimale Universelle - Indices composés détaillant l'analyse classificatrice.jpg|thumb|An explanatory schema of the Universal Decimal Classification index formation in French, 1920]]
The UDC was developed by the [[Belgium|Belgian]] bibliographers [[Paul Otlet]] and [[Henri La Fontaine]] at the end of the 19th century. In 1895, they created the Universal Bibliographic Repertory (''Répertoire Bibliographique Universel'') (RBU) which was intended to become a comprehensive classified index to all published information. The idea that the RBU should take the form of a card catalogue came from the young American zoologist [[Herbert Haviland Field]], who was at the time himself setting up a bibliographical agency in Zurich, the [[Concilium Bibliographicum]].<ref>Rayward, W. Boyd: From the index card to the World City: knowledge organization and visualization in the work and ideas of Paul Otlet. IN: A. Slavic, A. Akdag Salah and S. Davies (Eds.): Proceedings of the International UDC Seminar 2013: Classification & Visualization: Interfaces to Knowledge, The Hague (Netherlands), 24–25 October 2013. Wurzburg: Ergon Verlag, 2013, pp. 1-41</ref> A means of arranging the entries would be needed, and Otlet, having heard of the [[Dewey Decimal Classification]], wrote to Melvil Dewey and obtained permission to translate it into French. The idea outgrew the plan of mere translation, and a number of radical innovations were made, adapting the purely enumerative classification (in which all the subjects envisaged are already listed and coded) into one which allows for synthesis (that is, the construction of compound numbers to denote interrelated subjects that could never be exhaustively foreseen); various possible relations between subjects were identified, and symbols assigned to represent them. In its first edition in French "''Manuel du Répertoire bibliographique universel''" (1905), the UDC already included many features that were revolutionary in the context of knowledge classifications: tables of generally applicable (aspect-free) concepts—called common auxiliary tables; a series of special auxiliary tables with specific but re-usable attributes in a particular field of knowledge; an expressive notational system with connecting symbols and syntax rules to enable coordination of subjects and the creation of a documentation language proper.

The Universal Bibliographic Repertory grew to more than eleven million records in the period before [[World War I]]. The catalogue and its content organized by UDC can still be seen in [[Mundaneum]] in Mons, Belgium. In 2013 this catalogue was accepted onto the UNESCO [[Memory of the World Programme|Memory of the World international register]], recognising it as documentary heritage of global importance.<ref name="UNESCO Memory of the World Register">{{cite web|url=https://www.unesco.org/en/memory-world/universal-bibliographic-repertory |publisher=UNESCO Memory of the World Programme |title=Universal Bibliographic Repertory|access-date=2025-04-04}}</ref>

== The application of UDC ==
UDC is used in around 150,000 libraries in 130 countries and in many bibliographical services which require detailed content indexing. In a number of countries it is the main classification system for information exchange and is used in all types of libraries: public, school, academic and special libraries.<ref>{{cite journal |last1=Slavic |first1=A. |title=Use of the Universal Decimal Classification: a worldwide survey |journal=Journal of Documentation |date=2006 |volume=64 |issue=2 |pages=211–228 |doi=10.1108/00220410810858029 |language=en|hdl=10150/105579 }}</ref><ref name="UDC Users Worldwide">{{cite web |url=http://www.udcc.org/index.php/site/page?view=users_worldwide  |title=UDC Users Worldwide |website=UDC Consortium website}}</ref><ref name="UDC Countries">{{cite web |url=http://www.udcc.org/countries.htm |title=UDC Countries |website=UDC Consortium}}</ref>

UDC is also used in [[national bibliographies]] of around 30 countries. Examples of large databases indexed by UDC include:<ref name="Large collections">[http://www.udcc.org/index.php/site/page?view=collections Collections indexed by UDC], UDC Consortium website</ref> 
: NEBIS (The Network of Libraries and Information Centers in Switzerland) — 2.6 million records
: COBIB.SI (Slovenian National Union Catalogue) — 3.5 million records
: Hungarian National Union Catalogue (MOKKA) — 2.9 million records
: [[VINITI RAS]] database (All-Russian Scientific and Technical Information Institute of Russian Academy of Science) with 28 million records
: Meteorological & Geoastrophysical Abstracts (MGA) with 600 journal titles
: PORBASE (Portuguese National Bibliography) with 1.5 million records

UDC has traditionally been used for the indexing of scientific articles which was an important source of information of scientific output in the period predating electronic publishing. Collections of research articles in many countries covering decades of scientific output contain UDC codes.  Examples of journal articles indexed by UDC:
:UDC code '''663.12:57.06''' in the article "Yeast Systematics: from Phenotype to Genotype" in the  journal ''Food Technology and Biotechnology'' ({{ISSN|1330-9862}})<ref>{{cite journal |title=Yeast Systematics: from Phenotype to Genotype |journal=Food Technology and Biotechnology |url=http://www.ftb.pbf.hr/index.php/ftb/article/viewFile/243/241 |access-date=28 October 2018 |issn=1330-9862|quote=Example: Journal article indexed by UDC}}</ref>
:UDC code '''37.037:796.56''', provided in the article "The game method as means of interface of technical-tactical and psychological preparation in sports orienteering" in the Russian journal "''Pedagogico-psychological and medico-biological problems of the physical culture and sport''"  ({{ISSN|2070-4798}}).<ref>{{cite journal |title=The game method as means of interface of technical-tactical and psychological preparation in sports orienteering |journal=Pedagogico-psychological and Medico-biological Problems of the Physical Culture and Sport |url=http://www.kamgifk.ru/magazin/20_%283%29_2011/20_%283%29_2011_16.pdf   |access-date=28 October 2018  |language=ru  |issn=2070-4798 |quote=Example: Journal article indexed by UDC}}</ref>
:UDC code '''621.715:621.924:539.3''' in the article Residual Stress in Shot-Peened Sheets of AIMg4.5Mn Alloy - in the journal ''Materials and technology'' ({{ISSN|1580-2949}}).<ref>{{cite journal |title=Residual Stress in Shot-Peened Sheets of AIMg4.5Mn Alloy |journal=Materials and Technology |url=http://www.docstoc.com/docs/5320753/UDK-Pregledni-znanstveni-lanek-ISSN-MTAEC-M-MI-OVI |access-date=28 October 2018 |issn=1580-2949 |quote=Example: Journal article indexed by UDC}}</ref>
:
The design of UDC lends itself to machine readability, and the system has been used both with early automatic mechanical sorting devices, and modern library [[OPAC]]s.<ref>{{cite journal |last1=Slavic |first1=A. |title=The level of exploitation of Universal Decimal Classification in library OPACs: a pilot study |journal=Vjesnik Bibliotekara Hrvatske |date=December 2006 |volume=49 |issue=3–4 |pages=155–182 |language=en|hdl=10150/105346 }}</ref><ref>{{cite journal |last1=Slavic, A. |title=UDC in subject gateways: experiment or opportunity? |journal=Knowledge Organization |date=2006 |volume=33 |issue=2 |pages=67–85 |language=en|hdl=10150/105276 }}</ref> Since 1993, a standard version of UDC has been maintained and distributed in a [[database]] format: UDC Master Reference File (UDC MRF) which is updated and released regularly.<ref name="UDC MRF">[http://www.udcc.org/index.php/site/page?view=mrf UDC Master Reference File], UDC Consortium website</ref> The 2011 version of the MRF (released in 2012) contains over 70,000 classes.<ref name="UDC Fact Sheet"/> In the past full printed editions used to have around 220,000 subdivisions.<ref name="UDCS">{{cite web |url=http://www.udcc.org/udcsummary/php/index.php |title=Universal Decimal Classification Summary  |publisher=UDC Consortium |access-date=April 13, 2022}}</ref>

== UDC structure ==

=== Notation ===
A notation is a code commonly used in classification schemes to represent a class, i.e. a subject and its position in the hierarchy, to enable mechanical sorting and filing of subjects. UDC uses [[Arabic numerals]] arranged decimally. Every number is thought of as a decimal fraction with the initial decimal point omitted, which determines the filing order. An advantage of decimal notational systems is that they are infinitely extensible, and when new subdivisions are introduced, they need not disturb the existing allocation of numbers. For ease of reading, a UDC notation is usually punctuated after every third digit:
{| 
|- 
| style="width:18%; font-weight:bold;" | Notation || style="font-weight:bold;" | Caption (Class description)
|-
| 539.120 ||Theoretical problems of elementary particles physics. Theories and models of fundamental interactions
|-
| 539.120.2 || Symmetries of quantum physics
|-
|539.120.22 ||  Conservation laws
|-
| 539.120.222 ||   Translations. Rotations
|-
| 539.120.224 ||   Reflection in time and space
|-
|539.120.226 ||   Space-time symmetries
|-
| 539.120.23 ||  Internal symmetries
|-
| 539.120.3 || Currents
|-
| 539.120.4 || Unified field theories
|-
|539.120.5 || Strings
|}

In UDC the notation has two features that make the scheme easier to browse and work with: 
* '''hierarchically expressive''' – the longer the notation, the more specific the class: removing the final digit automatically produces a broader class code.
* '''syntactically expressive''' – when UDC codes are combined, the sequence of digits is interrupted by a precise type of punctuation sign which indicates that the expression is a combination of classes rather than a simple class e.g. the colon in 34:32 indicates that there are two distinct notational elements: 34 Law. Jurisprudence and 32 Politics; the closing and opening parentheses and double quotes in the following code 913(574.22)"19"(084.3) indicate four separate notational elements: 913 Regional geography, (574.22) North Kazakhstan (Soltüstik Qazaqstan); "19" 20th century and (084.3) Maps (document form)

=== Basic features and syntax ===
UDC is an analytico-synthetic and [[faceted classification]]. It allows an unlimited combination of attributes of a subject and relationships between subjects to be expressed. UDC codes from different tables can be combined to present various aspects of document content and form, e.g. 94(410)"19"(075) History ''(main subject)'' of United Kingdom ''(place)'' in 20th century ''(time)'', a textbook ''(document form)''. Or: 37:2 Relationship between Education and Religion. Complex UDC expressions can be accurately parsed into constituent elements.

UDC is also a disciplinary classification covering the entire universe of knowledge.<ref name="UDC Subject Coverage">[http://www.udcc.org/index.php/site/page?view=subject_coverage UDC Subject Coverage], UDC Consortium website</ref> This type of classification can also be described as ''aspect'' or ''perspective'', which means that concepts are subsumed and placed under the field in which they are studied. Thus, the same concept can appear in different fields of knowledge. This particular feature is usually implemented in UDC by re-using the same concept in various combinations with the main subject, e.g. a code for language in common auxiliaries of language is used to derive numbers for ethnic grouping, individual languages in linguistics and individual literatures. Or, a code from the auxiliaries of place, e.g. ''(410) United Kingdom'', uniquely representing the concept of United Kingdom can be used to express ''911(410) Regional geography of United Kingdom'' and ''94(410) History of United Kingdom''.

=== Organization of classes ===

Concepts are organized in two kinds of tables in UDC:<ref name="UDC Structure">[http://www.udcc.org/index.php/site/page?view=about_structure UDC Structure and Tables], UDC Consortium website</ref>

*'''Common auxiliary tables''' (including certain auxiliary signs). These tables contain facets of concepts representing general recurrent characteristics, applicable over a range of subjects throughout the main tables, including notions such as place, language of the text and physical form of the document, which may occur in almost any subject. UDC numbers from these tables, called common auxiliaries are simply added at the end of the number for the subject taken from the main tables. There are over 15,000 common auxiliaries in UDC.
*'''The main tables or main schedules''' containing the various disciplines and branches of knowledge are arranged in 9 main classes, numbered from 0 to 9 (with class 4 being vacant). At the beginning of each class there are also series of special auxiliaries, which express aspects that are recurrent within this specific class. Main tables in UDC contain more than 60,000 subdivisions.

==== Main classes ====
*0 [[Science]] and [[Knowledge]]. [[Organization]]. [[Computer Science]]. [[Information Science]]. [[Documentation]]. [[Librarianship]]. [[Institutions]]. [[Publications]]
*1 [[Outline of philosophy|Philosophy]]. [[Outline of psychology|Psychology]]
*2 [[Outline of religion|Religion]]. [[Outline of theology|Theology]]
*3 [[Outline of social science|Social Sciences]]
*4 ''vacant''
*5 [[Outline of mathematics|Mathematics]]. [[Outline of natural science|Natural Sciences]]
*6 [[Outline of applied science|Applied Sciences]]. [[Outline of medicine|Medicine]], [[Outline of technology|Technology]]
*7 [[The arts|The Arts]]. [[Outline of entertainment|Entertainment]]. [[Outline of sports|Sport]]
*8 [[Outline of linguistics|Linguistics]]. [[Outline of literature|Literature]]
*9 [[Outline of geography|Geography]]. [[Outline of history|History]]

The vacant class 4 is the result of a planned schedule expansion. This class was freed by moving linguistics into class 8 in the 1960s to make space for future developments in the rapidly expanding fields of knowledge; primarily natural sciences and technology.

==== Common auxiliary tables ====
''Common auxiliaries'' are aspect-free concepts that can be used in combination with any other UDC code from the main classes or with other common auxiliaries. They have unique notational representations that make them stand out in complex expressions. Common auxiliary numbers always begin with a certain symbol known as a facet indicator, e.g. <nowiki>=</nowiki> (equal sign) always introduces concepts representing the language of a document; (0...) numbers enclosed in parentheses starting with zero always represent a concept designating document form. Thus (075) Textbook and =111 English can be combined to express, e.g.(075)=111 Textbooks in English, and when combined with numbers from the main UDC tables they can be used as follows: 2(075)=111 Religion textbooks in English, 51(075)=111 Mathematics textbooks in English etc.

*=...	Common auxiliaries of language. Table 1c
*(0...)	Common auxiliaries of form. Table 1d
*(1/9)	Common auxiliaries of place. Table 1e
*(=...)	Common auxiliaries of human ancestry, ethnic grouping and nationality. Table 1f
*"..."	Common auxiliaries of time. Table 1g helps to make minute division of time e.g.:  "1993-1996"
*-0...	Common auxiliaries of general characteristics: Properties, Materials, Relations/Processes and Persons. Table 1k.
*-02	Common auxiliaries of properties. Table 1k
*-03	Common auxiliaries of materials. Table 1k
*-04	Common auxiliaries of relations, processes and operations. Table 1k
*-05	Common auxiliaries of persons and personal characteristics. Table 1k this table is repeated

==== Connecting signs ====
In order to preserve the precise meaning and enable accurate parsing of complex UDC expressions, a number of connecting symbols are made available to relate and extend UDC numbers. These are:
{| class="wikitable"
!Symbol !! Symbol name !! Meaning !! Example
|-
|<nowiki>+</nowiki> || [[Plus and minus signs|plus]] || coordination, addition || e.g. 59+636 [[zoology]] and [[animal breeding]]
|-
|<nowiki>/</nowiki> || [[Slash (punctuation)|stroke]] || consecutive extension || e.g. 592/599 Systematic zoology (everything from 592 to 599 inclusive)
|-
|<nowiki>:</nowiki> || [[Colon (punctuation)|colon]] || relation || e.g. 17:7  Relation of [[ethics]] to [[art]]
|-
|<nowiki>[ ]</nowiki> || square [[bracket]]s || subgrouping || e.g. 311:[622+669](485) [[statistics]] of [[mining]] and [[metallurgy]] in [[Sweden]] (the auxiliary qualifiers 622+669 considered as a unit)
|-
|<nowiki>*</nowiki> || asterisk || Introduces non-UDC notation  || e.g. 523.4*433 Planetology, minor planet Eros ([[International Astronomical Union|IAU]] authorized number after the asterisk)
|-
|<nowiki>A/Z</nowiki> || alphabetical extension || Direct alphabetical specification  || e.g. 821.133.1MOL French literature, works of Molière
|}

== UDC outline ==

<small>UDC classes in this outline are taken from the Multilingual Universal Decimal Classification Summary (UDCC Publication No. 088) released by the UDC Consortium under the Creative Commons Attribution Share Alike 3.0 license (first release 2009, subsequent update 2012).<ref name="UDCS" /></small>

=== Main tables ===

====0 [[Outline of science|Science]] and [[Outline of knowledge|knowledge]]. Organization. [[Outline of computer science|Computer science]]. Information. Documentation. Librarianship. Institution. Publications====

  00          Prolegomena. Fundamentals of knowledge and culture. Propaedeutics
  001         [[Outline of science|Science]] and [[Outline of knowledge|knowledge]] in general. Organization of intellectual work
  002         Documentation. Books. Writings. Authorship
  003         Writing systems and scripts
  004         [[Outline of computer science|Computer science]] and technology. Computing
  004.2       [[Computer architecture]]
  004.3       [[Computer hardware]]
  004.4       [[Software]]
  004.5       [[Human–computer interaction|Human-computer interaction]]
  004.6       Data
  004.7       Computer communication
  004.8       [[Outline of artificial intelligence|Artificial intelligence]]
  004.9       Application-oriented computer-based techniques
  005         [[Outline of business management|Management]]
  005.1       Management Theory
  005.2       Management agents. Mechanisms. Measures
  005.3       Management activities
  005.5       Management operations. Direction
  005.6       Quality management. Total quality management (TQM)
  005.7       Organizational management (OM)
  005.9       Fields of management
  005.92      Records management
  005.93      Plant management. Physical resources management
  005.94      [[Knowledge management]]
  005.95/.96  Personnel management. Human Resources management
  006         Standardization of products, operations, weights, measures and time
  007         Activity and organizing. Information. Communication and control theory generally (cybernetics)
  008         Civilization. [[Outline of culture|Culture]]. Progress   
  01          Bibliography and bibliographies. Catalogues
  02          Librarianship
  030         General reference works (as subject)
  050         Serial publications, periodicals (as subject)
  06          Organizations of a general nature
  069         [[Museum|Museums]]
  070         Newspapers (as subject). The Press. Outline of [[journalism]]
  08          Polygraphies. Collective works (as subject)
  09          Manuscripts. Rare and remarkable works (as subject)

====1 [[Outline of philosophy|Philosophy]]. [[Outline of psychology|Psychology]]====
  101        Nature and role of philosophy
  11         [[Metaphysics]]
  111        General metaphysics. Ontology
  122/129    Special Metaphysics
  13         Philosophy of mind and spirit. Metaphysics of spiritual life
  14         Philosophical systems and points of view
  141        Kinds  of viewpoint. Including:  Monism. Dualism. Pluralism. Ontological Materialism. Metaphysical Idealism. Platonism, etc.
  159.9      [[Outline of psychology|Psychology]]
  159.91     Psychophysiology (physiological psychology). Mental physiology
  159.92     Mental development and capacity. Comparative psychology
  159.93     Sensation. Sensory perception
  159.94     [[Executive functions]]
  159.95     Higher mental processes
  159.96     Special mental states and processes
  159.97     [[Abnormal psychology]]
  159.98     Applied psychology (psychotechnology) in general
  16         [[Outline of logic|Logic]]. [[Outline of epistemology|Epistemology]]. Theory of knowledge. Methodology of logic
  17         Moral philosophy. [[Outline of ethics|Ethics]]. Practical philosophy

====2 [[Outline of religion|Religion]]. [[Outline of theology|Theology]]====

<small>The UDC tables for religion are fully faceted. Indicated in italics below, are special auxiliary numbers that can be used to express attributes (facets) of any specific faith. Any special number can be combined with any religion e.g.  ''-5 Worship'' can be used to express e.g. ''26-5 Worship in Judaism'', ''27-5 Worship in Christianity'', ''24-5 Worship in Buddhism''. The complete special auxiliary tables contain around 2000 subdivisions of various attributes that can be attached to express various aspects of individual faiths to a great level of specificity allowing equal level of detail for every religion.</small>
  ''2-1/-9	Special auxiliary subdivision for religion''
  ''2-1	Theory and philosophy of religion. Nature of religion. Phenomenon of religion''
  ''2-2	Evidences of religion''
  ''2-3	Persons in religion''
  ''2-4	Religious activities. Religious practice''
  ''2-5	Worship broadly. Cult. Rites and ceremonies''
  ''2-6	Processes in religion''
  ''2-7	Religious organization and administration''
  ''2-8	Religions characterised by various properties''
  ''2-9	History of the faith, religion, denomination or church''
  21/29	Religious systems. Religions and faiths
  21	Prehistoric and primitive religions
  22	Religions originating in the Far East
  23	Religions originating in Indian sub-continent. Hindu religion in the broad sense
  24	[[Outline of Buddhism|Buddhism]]
  25	Religions of antiquity. Minor cults and religions
  26	[[Outline of Judaism|Judaism]]
  27	[[Outline of Christianity|Christianity]]
  28	[[Outline of Islam|Islam]]
  29	[[New religious movement|Modern spiritual movements]]

====3 [[Outline of social science|Social sciences]]====
  303   Methods of the social sciences
  304	Social questions. Social practice. Cultural practice. Way of life (Lebensweise)
  305	Gender studies
  308	Sociography. Descriptive studies of society (both qualitative and quantitative)
  311	[[Outline of statistics|Statistics]] as a science. Statistical theory
  314/316 [[Outline of society|Society]]
  314	Demography. Population studies
  316	[[Outline of sociology|Sociology]]
  32	[[Outline of politics|Politics]]
  33	[[Outline of economics|Economics]]. Economic science
  34	[[Outline of law|Law]]. Jurisprudence
  35	Public administration. Government. Military affairs
  36	Safeguarding the mental and material necessities of life
  37	[[Outline of education|Education]]
  39	Cultural anthropology. Ethnography. Customs. Manners. Traditions. Way of life

====4 Currently Vacant====

This section is currently vacant.

====5 [[Outline of mathematics|Mathematics]]. [[Outline of natural science|Natural sciences]]====
  502/504  Environmental science. Conservation of natural resources. Threats to the environment and protection against them
  502	The environment and its protection
  504	Threats to the environment
  51	[[Outline of mathematics|Mathematics]]
  510	Fundamental and general considerations of mathematics
  511	Number theory
  512	[[Outline of algebra|Algebra]]
  514	[[Outline of geometry|Geometry]]
  517	[[Mathematical analysis|Analysis]]
  519.1	[[Combinatorial analysis]]. [[Graph theory]]
  519.2	[[Outline of probability|Probability]]. Mathematical statistics
  519.6	Computational mathematics. [[Outline of numerical analysis|Numerical analysis]]
  519.7	Mathematical cybernetics
  519.8	Operational research (OR): mathematical theories and methods
  52	[[Outline of astronomy|Astronomy]]. Astrophysics. [[Outline of space exploration|Space research]]. Geodesy
  53	[[Outline of physics|Physics]]
  531/534  [[Mechanics]]
  535	[[Optics]]
  536	[[Heat]]. [[Thermodynamics]]. [[Statistical mechanics|Statistical physics]]
  537	[[Electricity]]. [[Magnetism]]. [[Electromagnetism]]
  538.9	[[Condensed matter physics]]. [[Solid-state physics|Solid state physics]]
  539	Physical nature of matter
  54	[[Outline of chemistry|Chemistry]]. Crystallography. Mineralogy
  542	Practical laboratory chemistry. Preparative and experimental chemistry
  543	[[Analytical chemistry]]
  544	[[Physical chemistry]]
  546	[[Inorganic chemistry]]
  547	[[Outline of organic chemistry|Organic chemistry]]
  548/549 Mineralogical sciences. Crystallography. Mineralogy
  55	[[Outline of earth science|Earth sciences]]. Geological sciences
  56	[[Paleontology]]
  57	Biological sciences in general
  58	[[Outline of botany|Botany]]
  59	[[Outline of zoology|Zoology]]

====6 [[Outline of applied science|Applied sciences]]. [[Outline of medicine|Medicine]]. [[Outline of technology|Technology]]====

<small>Class 6 occupies the largest proportion of UDC schedules. It contains over 44,000 subdivisions. Each specific field of technology or industry usually contains more than one special auxiliary table with concepts needed to express operations, processes, materials and products. As a result, UDC codes are often created through the combination of various attributes. Equally, some parts of this class enumerate concepts to a great level of detail e.g.  ''621.882.212 Hexagon screws with additional shapes. Including: Flank screws. Collar screws. Cap screws''
</small>

  60    [[Outline of biotechnology|Biotechnology]]
  61	Medical sciences
  611/612 [[Human biology]]
  613	Hygiene generally. Personal health and hygiene
  614	Public health and hygiene. Accident prevention
  615	[[Pharmacology]]. [[Therapeutics]]. [[Toxicology]]
  616	[[Pathology]]. [[Clinical medicine]]
  617	[[Surgery]]. [[Orthopaedics]]. [[Ophthalmology]]
  618	[[Gynaecology]]. [[Obstetrics]]
  62	[[Outline of engineering|Engineering]]. [[Outline of technology|Technology]] in general
  620	Materials testing. Commercial materials. Power stations. Economics of energy
  621	Mechanical engineering in general. Nuclear technology. Electrical engineering. Machinery
  622	[[Outline of mining|Mining]]
  623	[[Military engineering]]
  624	Civil and structural engineering in general
  625	Civil engineering of land transport. Railway engineering. Highway engineering
  626/627  Hydraulic engineering and construction. Water (aquatic) structures
  629	Transport vehicle engineering
  63	[[Outline of agriculture|Agriculture]] and related sciences and techniques. Forestry. Farming. Wildlife exploitation
  630	[[Forestry]]
  631/635	Farm management. Agronomy. Horticulture
  633/635	Horticulture in general. Specific crops
  636	Animal husbandry and breeding in general. Livestock rearing. Breeding of domestic animals
  64	Home economics. Domestic science. Housekeeping
  65	Communication and transport industries. Accountancy. Business management. Public relations
  654	Telecommunication and telecontrol (organization, services)
  655	Graphic industries. Printing. Publishing. Book trade
  656	Transport and postal services. Traffic organization and control
  657	[[Accounting|Accountancy]]
  658	[[Outline of business management|Business management]], administration. Commercial organization
  659	Publicity. Information work. [[Outline of public relations|Public relations]]
  66	Chemical technology. Chemical and related industries
  67	Various industries, trades and crafts
  68	Industries, crafts and trades for finished or assembled articles
  69	Building ([[Outline of construction|construction]]) trade. Building materials. Building practice and procedure

====7 The arts. Recreation. [[Outline of entertainment|Entertainment]]. [[Outline of sports|Sport]]====
  ''7.01/.09	Special auxiliary subdivision for the arts''
  ''7.01	Theory and philosophy of art. Principles of design, proportion, optical effect''
  ''7.02	Art technique. Craftsmanship''
  ''7.03	Artistic periods and phases. Schools, styles, influences''
  ''7.04	Subjects for artistic representation. Iconography. Iconology''
  ''7.05	Applications of art (in industry, trade, the home, everyday life)''
  ''7.06	Various questions concerning art''
  ''7.07	Occupations and activities associated with the arts and entertainment''
  ''7.08	Characteristic features, forms, combinations etc. (in art, entertainment and sport)''
  ''7.091	Performance, presentation (in original medium)''
  71	Physical planning. Regional, town and country planning. Landscapes, parks, gardens
  72	[[Outline of architecture|Architecture]]
  73	Plastic arts
  74	[[Outline of drawing and drawings|Drawing]]. [[Outline of design|Design]]. [[Outline of crafts|Applied arts and crafts]]
  745/749	Industrial and domestic arts and crafts. Applied arts
  75	[[Outline of painting|Painting]]
  76	Graphic art, printmaking. Graphics
  77	[[Outline of photography|Photography]] and similar processes
  78	[[Outline of music|Music]]
  79	Recreation. [[Outline of entertainment|Entertainment]]. [[Outline of games|Games]]. [[Outline of sports|Sport]]
  791	Cinema. [[Outline of film|Films]] (motion pictures)
  792	[[Outline of theatre|Theatre]]. [[Outline of stagecraft|Stagecraft]]. Dramatic performances
  793	Social entertainments and recreations. Art of movement. [[Outline of dance|Dance]]
  794	Board and table games (of thought, skill and chance)
  796	[[Outline of sports|Sport]]. [[Outline of games|Games]]. [[Outline of exercise|Physical exercises]]
  797	Water sports. Aerial sports
  798	Riding and driving. Horse and other animal sports
  799	Sport fishing. Sport hunting. Shooting and target sports

====8 Language. [[Outline of linguistics|Linguistics]]. [[Outline of literature|Literature]]====

<small>Tables for class 8 are fully faceted and details are expressed through combination with common auxiliaries of language (Table 1c) and a series of special auxiliary tables to indicate other facets or attributes in Linguistics or Literature. As a result, this class allows for great specificity in indexing although the schedules themselves occupy very little space in UDC. The subdivisions of e.g. ''811 Languages'' or ''821 Literature'' are derived from common auxiliaries of language =1/=9 (Table 1c) by substituting a point for the equals sign, e.g. 811.111 English language (as a subject of a linguistic study) and ''821.111 English literature'' derives from ''=111 English language''. Common auxiliaries of place and time are also frequently used in this class to express place and time facets of Linguistics or Literature, e.g. ''821.111(71)"18" English literature of Canada in 19th century''
</small>
  80	General questions relating to both linguistics and literature. Philology
  801	Prosody. Auxiliary sciences and sources of philology
  808	Rhetoric. The effective use of language  
  '''81	[[Outline of linguistics|Linguistics]] and languages'''
  ''81`1/`4	Special auxiliary subdivision for subject fields and facets of linguistics and languages''
 '' 81`1	General linguistics''
  ''81`2	[[Outline of semiotics|Theory of signs]]. Theory of translation. Standardization. Usage. Geographical linguistics''
  ''81`3	Mathematical and applied linguistics. Phonetics. Graphemics. Grammar. Semantics. Stylistics''
  ''81`4	Text linguistics, Discourse analysis. Typological linguistics''
  ''81`42	Text linguistics. Discourse analysis''
  ''81`44	Typological linguistics''
  811	Languages
        <small>Derived from the common auxiliaries of language =1/=9 (Table 1c) by replacing the equal sign = with prefix ''811.'' e.g. ''=111 English'' becomes ''811.111 Linguistics of English language''</small>
  811.1/.9	All languages natural or artificial
  811.1/.8	Individual natural languages
  811.1/.2	Indo-European languages
  811.21/.22	Indo-Iranian languages
  811.3	Dead languages of unknown affiliation. Caucasian languages
  811.4	Afro-Asiatic, Nilo-Saharan, Congo-Kordofanian, Khoisan languages
  811.5	Ural-Altaic, Palaeo-Siberian, Eskimo-Aleut, Dravidian and Sino-Tibetan languages. Japanese. Korean. Ainu
  811.6	Austro-Asiatic languages. Austronesian languages
  811.7	Indo-Pacific (non-Austronesian) languages. Australian languages
  811.8	American indigenous languages
  811.9	Artificial languages
  '''82	[[Outline of literature|Literature]]'''
  ''82-1/-9	Special auxiliary subdivision for literary forms, genres''
  ''82-1	[[Outline of poetry|Poetry]]. Poems. Verse''
  ''82-2	Drama. Plays''
  ''82-3	[[Outline of fiction|Fiction]]. Prose narrative''
  ''82-31	Novels. Full-length stories''
  ''82-32	Short stories. Novellas''
  ''82-4	Essays''
  ''82-5	Oratory. Speeches''
  ''82-6	Letters. Art of letter-writing. Correspondence. Genuine letters''
  ''82-7	Prose satire. Humour, epigram, parody''
  ''82-8	Miscellanea. Polygraphies. Selections''
  ''82-9	Various other literary forms''
  ''82-92	Periodical literature. Writings in serials, journals, reviews''
  ''82-94	History as literary genre. Historical writing. Historiography. Chronicles. Annals. Memoirs''
  ''82.02/.09	Special auxiliary subdivision for theory, study and technique of literature''
  ''82.02	Literary schools, trends and movements''
  ''82.09	Literary criticism. Literary studies''
  ''82.091	Comparative literary studies. Comparative literature''
  821	Literatures of individual languages and language families
        <small>Derived from the common auxiliaries of language =1/=9 (Table 1c) by replacing the equal sign = with prefix ''821.'' e.g. ''=111 English'' becomes ''821.111 English literature''</small>

====9 [[Outline of geography|Geography]]. Biography. [[Outline of history|History]]====

<small>Tables for Geography and History in UDC are fully faceted and place, time and ethnic grouping facets are expressed through combination with common auxiliaries of place (Table 1d), ethnic grouping (Table 1f) and time (Table 1g)
</small>

  902/908	Archaeology. Prehistory. Cultural remains. Area studies
  902	[[Outline of archaeology|Archaeology]]
  903	Prehistory. Prehistoric remains, artifacts, antiquities
  904	Cultural remains of historical times
  908	Area studies. Study of a locality
  91	[[Outline of geography|Geography]]. Exploration of the Earth and of individual countries. Travel. [[Outline of geography#Regional geography|Regional geography]]
  910	General questions. Geography as a science. Exploration. Travel
  911	General geography. Science of geographical factors (systematic geography). Theoretical geography
  911.2	[[Outline of geography#Physical geography|Physical geography]]
  911.3	[[Outline of geography#Human geography|Human geography]] (cultural geography). Geography of cultural factors
  911.5/.9	Theoretical geography
  912	Nonliterary, nontextual representations of a region
  913	[[Outline of geography#Regional geography|Regional geography]]
  92	Biographical studies. Genealogy. Heraldry. Flags
  929	Biographical studies
  929.5	Genealogy
  929.6	Heraldry
  929.7	Nobility. Titles. Peerage
  929.9	Flags. Standards. Banners
  93/94	[[Outline of history|History]]
  930	Science of history. Historiography
  930.1	History as a science
  930.2	Methodology of history. Ancillary historical sciences
  930.25	Archivistics. Archives (including public and other records)
  930.85	History of civilization. Cultural history
  94	General

=== Common auxiliary tables ===

====Common auxiliaries of language. Table 1c====
  =1/=9	Languages (natural and artificial)
  =1/=8	Natural languages
  =1/=2	Indo-European languages
  =1	Indo-European languages of Europe
  =11	Germanic languages
  =12	Italic languages
  =13	Romance languages
  =14	Greek (Hellenic)
  =15	Celtic languages
  =16	Slavic languages
  =17	Baltic languages
  =18	Albanian
  =19	Armenian
  =2	Indo-Iranian, Nuristani (Kafiri) and dead Indo-European languages
  =21/=22	Indo-Iranian languages
  =21	Indic languages
  =22	Iranian languages
  =29	Dead Indo-European languages (not listed elsewhere)
  =3	Dead languages of unknown affiliation. Caucasian languages
  =34	Dead languages of unknown affiliation, spoken in the Mediterranean and Near East (except Semitic)
  =35	Caucasian languages
  =4	Afro-Asiatic, Nilo-Saharan, Congo-Kordofanian, Khoisan languages
  =41	Afro-Asiatic (Hamito-Semitic) languages
  =42	Nilo-Saharan languages
  =43	Congo-Kordofanian (Niger-Kordofanian) languages
  =45	Khoisan languages
  =5	Ural-Altaic, Palaeo-Siberian, Eskimo-Aleut, Dravidian and Sino-Tibetan languages. Japanese. Korean. Ainu
  =51	Ural-Altaic languages
  =521	Japanese
  =531	Korean
  =541	Ainu
  =55	Palaeo-Siberian languages
  =56	Eskimo-Aleut languages
  =58	Sino-Tibetan languages
  =6	Austro-Asiatic languages. Austronesian languages
  =61	Austro-Asiatic languages
  =62	Austronesian languages
  =7	Indo-Pacific (non-Austronesian) languages. Australian languages
  =71	Indo-Pacific (non-Austronesian) languages
  =72	Australian languages
  =8	American indigenous languages
  =81	Indigenous languages of Canada, USA and Northern-Central Mexico
  =82	Indigenous languages of western North American Coast, Mexico and Yucatán
  =84/=88	Central and South American indigenous languages
  =84	Ge-Pano-Carib languages. Macro-Chibchan languages
  =85	Andean languages. Equatorial languages
  =86	Chaco languages. Patagonian and Fuegian languages
  =88	Isolated, unclassified Central and South American indigenous languages
  =9	Artificial languages
  =92	Artificial languages for use among human beings. International auxiliary languages (interlanguages)
  =93	Artificial languages used to instruct machines. Programming languages. Computer languages

====(0...) Common auxiliaries of form. Table 1d====
  ''(0.02/.08)	Special auxiliary subdivision for document form''
  ''(0.02)	Documents according to physical, external form''
  ''(0.03)	Documents according to method of production''
  ''(0.032)	Handwritten documents (autograph, holograph copies). Manuscripts. Pictorial documents (drawings, paintings)''
  ''(0.034)	Machine-readable documents''
  ''(0.04)	Documents according to stage of production''
  ''(0.05)	Documents for particular kinds of user''
  ''(0.06)	Documents according to level of presentation and availability''
  ''(0.07)	Supplementary matter issued with a document''
  ''(0.08)	Separately issued supplements or parts of documents''
  (01)	Bibliographies
  (02)	Books in general
  (03)	Reference works
  (04)	Non-serial separates. Separata
  (041)	Pamphlets. Brochures
  (042)	Addresses. Lectures. Speeches
  (043)	Theses. Dissertations
  (044)	Personal documents. Correspondence. Letters. Circulars
  (045)	Articles in serials, collections etc. Contributions
  (046)	Newspaper articles
  (047)	Reports. Notices. Bulletins
  (048)	Bibliographic descriptions. Abstracts. Summaries. Surveys
  (049)	Other non-serial separates
  (05)	Serial publications. Periodicals
  (06)	Documents relating to societies, associations, organizations
  (07)	Documents for instruction, teaching, study, training
  (08)	Collected and polygraphic works. Forms. Lists. Illustrations. Business publications
  (09)	Presentation in historical form. Legal and historical sources
  (091)	Presentation in chronological, historical form. Historical presentation in the strict sense
  (092)	Biographical presentation
  (093)	Historical sources
  (094)	Legal sources. Legal documents

====(1/9) Common auxiliaries of place. Table 1e====
  (1)	Place and space in general. Localization. Orientation
  ''(1-0/-9)	Special auxiliary subdivision for boundaries and spatial forms of various kinds''
  ''(1-0)	Zones''
  ''(1-1)	Orientation. Points of the compass. Relative position''
  ''(1-11)	East. Eastern''
  ''(1-13)	South. Southern''
  ''(1-14)	South-west. South-western''
  ''(1-15)	West. Western''
  ''(1-17)	North. Northern''
  ''(1-19)	Relative location, direction and orientation''
  ''(1-2)	Lowest administrative units. Localities''
  ''(1-5)	Dependent or semi-dependent territories''
  ''(1-6)	States or groupings of states from various points of view''
  ''(1-7)	Places and areas according to privacy, publicness and other special features''
  ''(1-8)	Location. Source. Transit. Destination''
  ''(1-9)	Regionalization according to specialized points of view''
  (100)	Universal as to place. International. All countries in general
  (2)	Physiographic designation
  (20)	Ecosphere
  (21)	Surface of the Earth in general. Land areas in particular. Natural zones and regions
  (23)	Above sea level. Surface relief. Above ground generally. Mountains
  (24)	Below sea level. Underground. Subterranean
  (25)	Natural flat ground (at, above or below sea level). The ground in its natural condition, cultivated or inhabited
  (26)	Oceans, seas and interconnections
  (28)	Inland waters
  (29)	The world according to physiographic features
  (3)	Places of the ancient and mediaeval world
  (31)	Ancient China and Japan
  (32)	[[Outline of ancient Egypt|Ancient Egypt]]
  (33)	Ancient Roman Province of Judaea. The Holy Land. Region of the Israelites
  (34)	[[Outline of ancient India|Ancient India]]
  (35)	Medo-Persia
  (36)	Regions of the so-called barbarians
  (37)	Italia. [[Outline of ancient Rome|Ancient Rome]] and Italy
  (38)	[[Outline of ancient Greece|Ancient Greece]]
  (399)	Other regions. Ancient geographical divisions other than those of classical antiquity
  (4/9)	Countries and places of the modern world
  (4)	[[Outline of Europe|Europe]]
  (5)	[[Outline of Asia|Asia]]
  (6)	[[Outline of Africa|Africa]]
  (7)	[[Outline of North America|North]] and Central America
  (8)	[[Outline of South America|South America]]
  (9)	States and regions of the South Pacific and [[Outline of Australia|Australia]]. Arctic. Antarctic

====(=...) Common auxiliaries of human ancestry, ethnic grouping and nationality. Table 1f====

<small>''They are derived mainly from the common auxiliaries of language =... (Table 1c) and so may also usefully distinguish linguistic-cultural groups, e.g. =111 English is used to represent (=111) English speaking peoples''</small>

  (=01)	Human ancestry groups
  (=011)	European Continental Ancestry Group
  (=012)	Asian Continental Ancestry Group
  (=013)	African Continental Ancestry Group
  (=014)	Oceanic Ancestry Group
  (=017)	American Native Continental Ancestry Group
  (=1/=8)	Linguistic-cultural groups, ethnic groups, peoples ['''derived from Table 1c''']
  (=1:1/9)	Peoples associated with particular places
                ''e.g. (=111:71) Anglophone population of Canada''

===="..." Common auxiliaries of time. Table 1g====
  "0/2"	Dates and ranges of time (CE or AD) in conventional Christian (Gregorian) reckoning
  "0"	First millennium CE
  "1"	Second millennium CE
  "2"	Third millennium CE
  "3/7"	Time divisions other than dates in Christian (Gregorian) reckoning
  "3"	Conventional time divisions and subdivisions: numbered, named, etc.
  "4"	Duration. Time-span. Period. Term. Ages and age-groups
  "5"	Periodicity. Frequency. Recurrence at specified intervals.
  "6"	Geological, archaeological and cultural time divisions
  "61/62" Geological time division
  "63"	Archaeological, prehistoric, protohistoric periods and ages
  "67/69" Time reckonings: universal, secular, non-Christian religious
  "67"	Universal time reckoning. Before Present
  "68"	Secular time reckonings other than universal and the Christian (Gregorian) calendar
  "69"	Dates and time units in non-Christian (non-Gregorian) religious time reckonings
  "7"	Phenomena in time. Phenomenology of time

====-0 Common auxiliaries of general characteristics. Table 1k====
  '''-02	Common auxiliaries of properties'''
  -021	Properties of existence
  -022	Properties of magnitude, degree, quantity, number, temporal values, dimension, size
  -023	Properties of shape
  -024	Properties of structure. Properties of position
  -025	Properties of arrangement
  -026	Properties of action and movement
  -027	Operational properties
  -028	Properties of style and presentation
  -029	Properties derived from other main classes
  '''-03 Common auxiliaries of materials'''
  -032	Naturally occurring mineral materials
  -033	Manufactured mineral-based materials
  -034	Metals
  -035	Materials of mainly organic origin
  -036	Macromolecular materials. Rubbers and plastics
  -037	Textiles. Fibres. Yarns. Fabrics. Cloth
  -039	Other materials
  '''-04 Common auxiliaries of relations, processes and operations'''
  -042	Phase relations
  -043	General processes
  -043.8/.9 Processes of existence
  -045	Processes related to position, arrangement, movement, physical properties, states of matter
  -047/-049	General operations and activities
  '''-05 Common auxiliaries of persons and personal characteristics'''
  -051	Persons as agents, doers, practitioners (studying, making, serving etc.)
  -052	Persons as targets, clients, users (studied, served etc.)
  -053	Persons according to age or age-groups
  -054	Persons according to ethnic characteristics, nationality, citizenship etc.
  -055	Persons according to gender and kinship
  -056	Persons according to constitution, health, disposition, hereditary or other traits
  -057	Persons according to occupation, work, livelihood, education
  -058	Persons according to social class, civil status

==See also==
===Special classifications based on or used in combination with UDC===
*[[Lonclass|BBC LonClass]]

===Other faceted classifications===
*[[Bliss bibliographic classification]]
*[[Colon classification]]

===Other library classifications===
*[[Dewey Decimal Classification]]
*[[Library of Congress Classification]]
*[[Chinese Library Classification]]
*[[Harvard-Yenching Classification]]

==References==
{{reflist}}

==External links==
{{wikidata property|P1190}}
*[http://www.udcc.org/ Universal Decimal Classification Consortium]
**[http://www.udcc.org/about.htm About Universal Decimal Classification]
**[http://www.udcc.org/udcsummary/php/index.php Multilingual UDC Summary]
**[http://udcdata.info/ UDC Linked Data]

{{Library classification systems}}

{{Authority control}}

[[Category:Belgian inventions]]
[[Category:Controlled vocabularies]]
[[Category:Decimal classification systems]]
[[Category:Library cataloging and classification]]