Universal Decimal Classification
The Universal Decimal Classification 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. The UDC is an analytico-synthetic and faceted classification system featuring detailed vocabulary and syntax that enables powerful content indexing and information retrieval in large collections. Since 1991, the UDC has been owned and managed by the UDC Consortium, 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. UDC Summary, an abridged Web version of the scheme, is available in over 50 languages. 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.
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. UDC codes can describe any type of document or object to any desired level of detail. These can include textual documents and other media such as films, video and sound recordings, illustrations, maps as well as realia such as museum objects.
History
The UDC was developed by the Belgian bibliographers Paul Otlet and Henri La Fontaine at the end of the 19th century. In 1895, they created the Universal Bibliographic Repertory 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. 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 into one which allows for synthesis ; various possible relations between subjects were identified, and symbols assigned to represent them. In its first edition in French, Manuel du Répertoire bibliographique universel, the UDC already included many features that were revolutionary in the context of knowledge classifications: tables of generally applicable 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 international register, recognising it as documentary heritage of global importance.
Application
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.UDC is also used in national bibliographies of around 30 countries. Examples of large databases indexed by UDC include:
- NEBIS — 2.6 million records
- COBIB.SI — 3.5 million records
- Hungarian National Union Catalogue — 2.9 million records
- VINITI RAS database with 28 million records
- Meteorological & Geoastrophysical Abstracts with 600 journal titles
- PORBASE with 1.5 million records
- UDC code in the article "Yeast Systematics: from Phenotype to Genotype" in the journal Food Technology and Biotechnology
- UDC code, 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" .
- UDC code in the article Residual Stress in Shot-Peened Sheets of AIMg4.5Mn Alloy - in the journal Materials and technology.
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: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. For example, the colon in indicates that there are two distinct notational elements: Law. Jurisprudence and Politics. In the following code, the parentheses and quotes indicate four separate notational elements: Regional geography, North Kazakhstan, 20th century and Maps .
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. History of United Kingdom in 20th century, a textbook. Or: 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. 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. United Kingdom, uniquely representing the concept of United Kingdom can be used to express Regional geography of United Kingdom and History of United Kingdom.
Organization
Concepts are organized in two kinds of tables:- Common auxiliary tables. 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. 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 Philosophy. Psychology
- 2 Religion. Theology
- 3 Social Sciences
- 4 vacant
- 5 Mathematics. Natural Sciences
- 6 Applied Sciences. Medicine, Technology
- 7 The Arts. Entertainment. Sport
- 8 Linguistics. Literature
- 9 Geography. History
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. For example, an equals sign always indicates a language; numbers starting with zero and enclosed in parentheses always indicate a document form. Thus Textbook and English can be combined to express, for example, Textbooks in English. When combined with numbers from the main UDC tables one might get: Religion textbooks in English or Mathematics textbooks in English.| Indicator | Table | Concepts |
| 1c | Language | |
| 1d | Form | |
| 1e | Place | |
| 1f | Human ancestry, ethnic grouping and nationality | |
| 1g | Time | |
| 1k | Properties | |
| 1k | Materials | |
| 1k | Relations, processes and operations | |
| 1k | Persons and personal characteristics |
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:| Symbol | Symbol name | Meaning | Example |
| plus | coordination, addition | zoology and animal breeding | |
| stroke | consecutive extension | Systematic zoology | |
| colon | relation | Relation of ethics to art | |
| square brackets | subgrouping | statistics of mining and metallurgy in Sweden | |
| asterisk | Introduces non-UDC notation | Planetology, minor planet Eros | |
| alphabetical extension | Direct alphabetical specification | French literature, works of Molière |
Outline
UDC classes in this outline are taken from the Multilingual Universal Decimal Classification Summary released by the UDC Consortium under the Creative Commons Attribution Share Alike 3.0 license.Main tables
0 Science and knowledge. Organization. Computer science. Information. Documentation. Librarianship. Institution. Publications
| Class | Description |
| Prolegomena. Fundamentals of knowledge and culture. Propaedeutics | |
| Science and knowledge in general. Organization of intellectual work | |
| Documentation. Books. Writings. Authorship | |
| Writing systems and scripts | |
| Computer science and technology. Computing | |
| Computer architecture | |
| Computer hardware | |
| Software | |
| Human-computer interaction | |
| Data | |
| Computer communication | |
| Artificial intelligence | |
| Application-oriented computer-based techniques | |
| Management | |
| Management Theory | |
| Management agents. Mechanisms. Measures | |
| Management activities | |
| Management operations. Direction | |
| Quality management. Total quality management | |
| Organizational management | |
| Fields of management | |
| Records management | |
| Plant management. Physical resources management | |
| Knowledge management | |
| Personnel management. Human Resources management | |
| Standardization of products, operations, weights, measures and time | |
| Activity and organizing. Information. Communication and control theory generally | |
| Civilization. Culture. Progress | |
| Bibliography and bibliographies. Catalogues | |
| Librarianship | |
| General reference works | |
| Serial publications, periodicals | |
| Organizations of a general nature | |
| Museums | |
| Newspapers. The Press. Outline of journalism | |
| Polygraphies. Collective works | |
| Manuscripts. Rare and remarkable works |
2 Religion. Theology
The UDC tables for religion are fully faceted. The second table below lists special auxiliary numbers that can be used to express attributes of any specific faith. Any special number can be combined with any religion e.g. Worship can be used to express, for example, Worship in Judaism, Worship in Christianity, or 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.| Class | Description |
| Religious systems. Religions and faiths | |
| Prehistoric and primitive religions | |
| Religions originating in the Far East | |
| Religions originating in Indian sub-continent. Hindu religion in the broad sense | |
| Buddhism | |
| Religions of antiquity. Minor cults and religions | |
| Judaism | |
| Christianity | |
| Islam | |
| Modern spiritual movements |
| Class | Description |
| Theory and philosophy of religion. Nature of religion. Phenomenon of religion | |
| Evidences of religion | |
| Persons in religion | |
| Religious activities. Religious practice | |
| Worship broadly. Cult. Rites and ceremonies | |
| Processes in religion | |
| Religious organization and administration | |
| Religions characterised by various properties | |
| History of the faith, religion, denomination or church |
4 Currently Vacant
This section is currently vacant.6 Applied sciences. Medicine. Technology
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, for example, Hexagon screws with additional shapes. Including: Flank screws. Collar screws. Cap screws| Class | Description |
| Biotechnology | |
| Medical sciences | |
| Human biology | |
| Hygiene generally. Personal health and hygiene | |
| Public health and hygiene. Accident prevention | |
| Pharmacology. Therapeutics. Toxicology | |
| Pathology. Clinical medicine | |
| Surgery. Orthopaedics. Ophthalmology | |
| Gynaecology. Obstetrics | |
| Engineering. Technology in general | |
| Materials testing. Commercial materials. Power stations. Economics of energy | |
| Mechanical engineering in general. Nuclear technology. Electrical engineering. Machinery | |
| Mining | |
| Military engineering | |
| Civil and structural engineering in general | |
| Civil engineering of land transport. Railway engineering. Highway engineering | |
| Hydraulic engineering and construction. Water structures | |
| Transport vehicle engineering | |
| Agriculture and related sciences and techniques. Forestry. Farming. Wildlife exploitation | |
| Forestry | |
| Farm management. Agronomy. Horticulture | |
| Horticulture in general. Specific crops | |
| Animal husbandry and breeding in general. Livestock rearing. Breeding of domestic animals | |
| Home economics. Domestic science. Housekeeping | |
| Communication and transport industries. Accountancy. Business management. Public relations | |
| Telecommunication and telecontrol | |
| Graphic industries. Printing. Publishing. Book trade | |
| Transport and postal services. Traffic organization and control | |
| Accountancy | |
| Business management, administration. Commercial organization | |
| Publicity. Information work. Public relations | |
| Chemical technology. Chemical and related industries | |
| Various industries, trades and crafts | |
| Industries, crafts and trades for finished or assembled articles | |
| Building trade. Building materials. Building practice and procedure |
7 The arts. Recreation. Entertainment. Sport
| Class | Description |
| Theory and philosophy of art. Principles of design, proportion, optical effect | |
| Art technique. Craftsmanship | |
| Artistic periods and phases. Schools, styles, influences | |
| Subjects for artistic representation. Iconography. Iconology | |
| Applications of art | |
| Various questions concerning art | |
| Occupations and activities associated with the arts and entertainment | |
| Characteristic features, forms, combinations etc. | |
| Performance, presentation |
8 Language. Linguistics. Literature
Tables for class 8 are fully faceted and details are expressed through combination with common auxiliaries of language 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 Languages or Literature, for example, are derived from common auxiliaries of language by substituting a point for the equals sign. Thus English language and English literature derive from 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. English literature of Canada in the 19th century.| Class | Description |
| General questions relating to both linguistics and literature. Philology | |
| Prosody. Auxiliary sciences and sources of philology | |
| Rhetoric. The effective use of language | |
| Linguistics and languages | |
Languages Derived from the common auxiliaries of language by replacing the equals sign with prefix. E.g. English becomes Linguistics of English language. | |
| All languages natural or artificial | |
| Individual natural languages | |
| Indo-European languages | |
| Indo-Iranian languages | |
| Dead languages of unknown affiliation. Caucasian languages | |
| Afro-Asiatic, Nilo-Saharan, Congo-Kordofanian, Khoisan languages | |
| Ural-Altaic, Palaeo-Siberian, Eskimo-Aleut, Dravidian and Sino-Tibetan languages. Japanese. Korean. Ainu | |
| Austro-Asiatic languages. Austronesian languages | |
| Indo-Pacific languages. Australian languages | |
| American indigenous languages | |
| Artificial languages | |
| Literature | |
Literatures of individual languages and language families Derived from the common auxiliaries of language by replacing the equals sign with prefix. E.g. English becomes English literature. |
| Class | Description |
| General linguistics | |
| Theory of signs. Theory of translation. Standardization. Usage. Geographical linguistics | |
| Mathematical and applied linguistics. Phonetics. Graphemics. Grammar. Semantics. Stylistics | |
| Text linguistics, Discourse analysis. Typological linguistics | |
| Text linguistics. Discourse analysis | |
| Typological linguistics |
| Class | Description |
| Poetry. Poems. Verse | |
| Drama. Plays | |
| Fiction. Prose narrative | |
| Novels. Full-length stories | |
| Short stories. Novellas | |
| Essays | |
| Oratory. Speeches | |
| Letters. Art of letter-writing. Correspondence. Genuine letters | |
| Prose satire. Humour, epigram, parody | |
| Miscellanea. Polygraphies. Selections | |
| Various other literary forms | |
| Periodical literature. Writings in serials, journals, reviews | |
| History as literary genre. Historical writing. Historiography. Chronicles. Annals. Memoirs |
| Class | Description |
| Literary schools, trends and movements | |
| Literary criticism. Literary studies | |
| Comparative literary studies. Comparative literature |
9 Geography. Biography. History
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, ethnic grouping and time| Class | Description |
| Archaeology. Prehistory. Cultural remains. Area studies | |
| Archaeology | |
| Prehistory. Prehistoric remains, artifacts, antiquities | |
| Cultural remains of historical times | |
| Area studies. Study of a locality | |
| Geography. Exploration of the Earth and of individual countries. Travel. Regional geography | |
| General questions. Geography as a science. Exploration. Travel | |
| General geography. Science of geographical factors. Theoretical geography | |
| Physical geography | |
| Human geography. Geography of cultural factors | |
| Theoretical geography | |
| Nonliterary, nontextual representations of a region | |
| Regional geography | |
| Biographical studies. Genealogy. Heraldry. Flags | |
| Biographical studies | |
| Genealogy | |
| Heraldry | |
| Nobility. Titles. Peerage | |
| Flags. Standards. Banners | |
| History | |
| Science of history. Historiography | |
| History as a science | |
| Methodology of history. Ancillary historical sciences | |
| Archivistics. Archives | |
| History of civilization. Cultural history | |
| General |
Common auxiliary tables
Table 1c: Language
| Class | Description |
| Languages | |
| Natural languages | |
| Indo-European languages | |
| Indo-European languages of Europe | |
| Germanic languages | |
| Italic languages | |
| Romance languages | |
| Greek | |
| Celtic languages | |
| Slavic languages | |
| Baltic languages | |
| Albanian | |
| Armenian | |
| Indo-Iranian, Nuristani and dead Indo-European languages | |
| Indo-Iranian languages | |
| Indic languages | |
| Iranian languages | |
| Dead Indo-European languages | |
| Dead languages of unknown affiliation. Caucasian languages | |
| Dead languages of unknown affiliation, spoken in the Mediterranean and Near East | |
| Caucasian languages | |
| Afro-Asiatic, Nilo-Saharan, Congo-Kordofanian, Khoisan languages | |
| Afro-Asiatic languages | |
| Nilo-Saharan languages | |
| Congo-Kordofanian languages | |
| Khoisan languages | |
| Ural-Altaic, Palaeo-Siberian, Eskimo-Aleut, Dravidian and Sino-Tibetan languages. Japanese. Korean. Ainu | |
| Ural-Altaic languages | |
| Japanese | |
| Korean | |
| Ainu | |
| Palaeo-Siberian languages | |
| Eskimo-Aleut languages | |
| Sino-Tibetan languages | |
| Austro-Asiatic languages. Austronesian languages | |
| Austro-Asiatic languages | |
| Austronesian languages | |
| Indo-Pacific languages. Australian languages | |
| Indo-Pacific languages | |
| Australian languages | |
| American indigenous languages | |
| Indigenous languages of Canada, USA and Northern-Central Mexico | |
| Indigenous languages of western North American Coast, Mexico and Yucatán | |
| Central and South American indigenous languages | |
| Ge-Pano-Carib languages. Macro-Chibchan languages | |
| Andean languages. Equatorial languages | |
| Chaco languages. Patagonian and Fuegian languages | |
| Isolated, unclassified Central and South American indigenous languages | |
| Artificial languages | |
| Artificial languages for use among human beings. International auxiliary languages | |
| Artificial languages used to instruct machines. Programming languages. Computer languages |
Table 1d: Form
| Class | Description |
| Documents according to physical, external form | |
| Documents according to method of production | |
| Handwritten documents. Manuscripts. Pictorial documents | |
| Machine-readable documents | |
| Documents according to stage of production | |
| Documents for particular kinds of user | |
| Documents according to level of presentation and availability | |
| Supplementary matter issued with a document | |
| Separately issued supplements or parts of documents |
Table 1e: Place
| Class | Description |
| Place and space in general. Localization. Orientation | |
| Universal as to place. International. All countries in general | |
| Physiographic designation | |
| Ecosphere | |
| Surface of the Earth in general. Land areas in particular. Natural zones and regions | |
| Above sea level. Surface relief. Above ground generally. Mountains | |
| Below sea level. Underground. Subterranean | |
| Natural flat ground. The ground in its natural condition, cultivated or inhabited | |
| Oceans, seas and interconnections | |
| Inland waters | |
| The world according to physiographic features | |
| Places of the ancient and mediaeval world | |
| Ancient China and Japan | |
| Ancient Egypt | |
| Ancient Roman Province of Judaea. The Holy Land. Region of the Israelites | |
| Ancient India | |
| Medo-Persia | |
| Regions of the so-called barbarians | |
| Italia. Ancient Rome and Italy | |
| Ancient Greece | |
| Other regions. Ancient geographical divisions other than those of classical antiquity | |
| Countries and places of the modern world | |
| Europe | |
| Asia | |
| Africa | |
| North and Central America | |
| South America | |
| States and regions of the South Pacific and Australia. Arctic. Antarctic |
| Class | Description |
| Zones | |
| Orientation. Points of the compass. Relative position | |
| East. Eastern | |
| South. Southern | |
| South-west. South-western | |
| West. Western | |
| North. Northern | |
| Relative location, direction and orientation | |
| Lowest administrative units. Localities | |
| Dependent or semi-dependent territories | |
| States or groupings of states from various points of view | |
| Places and areas according to privacy, publicness and other special features | |
| Location. Source. Transit. Destination | |
| Regionalization according to specialized points of view |
Table 1f: Human ancestry and grouping
They are derived mainly from the common auxiliaries of language and so may also usefully distinguish linguistic-cultural groups. For example English is used to represent English speaking peoples.| Class | Description |
| Human ancestry groups | |
| European Continental Ancestry Group | |
| Asian Continental Ancestry Group | |
| African Continental Ancestry Group | |
| Oceanic Ancestry Group | |
| American Native Continental Ancestry Group | |
| Linguistic-cultural groups, ethnic groups, peoples | |
Peoples associated with particular places E.g. Anglophone population of Canada |
Table 1g: Time
| Class | Description |
| Dates and ranges of time in conventional Christian reckoning | |
| First millennium CE | |
| Second millennium CE | |
| Third millennium CE | |
| Time divisions other than dates in Christian reckoning | |
| Conventional time divisions and subdivisions: numbered, named, etc. | |
| Duration. Time-span. Period. Term. Ages and age-groups | |
| Periodicity. Frequency. Recurrence at specified intervals. | |
| Geological, archaeological and cultural time divisions | |
| Geological time division | |
| Archaeological, prehistoric, protohistoric periods and ages | |
| Time reckonings: universal, secular, non-Christian religious | |
| Universal time reckoning. Before Present | |
| Secular time reckonings other than universal and the Christian calendar | |
| Dates and time units in non-Christian religious time reckonings | |
| Phenomena in time. Phenomenology of time |