Universel Decimal Classification,
Paul Otlet and Henri La Fontaine,
The UDC was developed by the Belgian bibliographers Paul Otlet and Henri La Fontaine at the end of 19th Century. In 1895, they created 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. A means of arranging the entries would be needed, and Otlet, having heard of 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 itself has developed into a remarkable information resource. In the period before World War I it grew to more than 11 million records. The catalogue and its content organized by UDC can still be seen in Mundaneum in Mons, Belgium (in 2013 recommended for inclusion in the UNESCO Memory of the World
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 type 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 (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)
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).
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).
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 OPACs. 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. The 2011 version of the MRF (released in 2012) contains over 70,000 classes. In the past full printed editions used to have around 220,000 subdivisions.
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:
Notation 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
539.120.4 Unified field theories
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 Edit
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. 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 Edit
Concepts are organized in two kinds of tables in UDC:
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 of common auxiliaries in UDC.
The main tables or main schedules containing the various disciplines and branches of knowledge, 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 Edit
0 Science and Knowledge. Organization. Computer Science. Information Science. Documentation. Librarianship. Institutions. Publications
1 Philosophy. Psychology
2 Religion. Theology
3 Social Sciences
5 Mathematics. Natural Sciences
6 Applied Sciences. Medicine, Technology
7 The Arts. Entertainment. Sport
8 Linguistics. Literature
9 Geography. 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 Edit
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 makes them stand out in complex expressions. Common auxiliary numbers always begin with a certain symbol known as a facet indicator, e.g. = (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 Edit
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.