Universal Decimal Classification

The Universal Decimal Classification or CDU is a bibliographic classification system in which all human knowledge takes place, both materially and conceptually.

This classification system was adapted by Paul Otlet and Henri La Fontaine from the Dewey System of Classification with permission from Melvil Dewey himself. CDU was first published in French in 1905, under the title Manuel du Repertoire Bibliographique Universel and was based on the fifth edition of Dewey's decimal classification. Since then it has been continually revised. and developed and has proven to be a very flexible and effective system for classifying and ordering bibliographic holdings. The last printed edition in Spanish is from 2015.

Characteristics of the classification

Universal decimal classification labels at the Maison Losseau.

CDU is a classification:

• Decimal: because it is ordered by the principle of decimal numbers (from 0 to 9).
• Universal: because it encompasses all human knowledge.
• Faceted: the material of the document depends on the aspect/matiz that is chosen.
• Hierarchical: Each subdivision can be subdivided into its logical components.
• Synthetics: the classes listed are blocks on which the composite and complex classes are built by means of various synthetic notational resources that it possesses.

CDU Structure

Main tables

Following the decimal scheme outlined by Dewey, CDU is structured into the following ten main classes:

• 0: Generalities. Science and knowledge. Organization. Information. Documentation. Encyclopedia. Bibliotheconomy. Institutions. Documents and publications
• 1: Philosophy. Psychology
• 2: Religion. Theology
• 3: Social sciences. Statistics. Politics. Economy. Trade. Right. Government. Military affairs. Social welfare. Sure. Education. Folclore
• 4: Vacant
• 5: Mathematics. Natural Sciences (including special assistants and main division)
• 6: Applied sciences. Medicine. Technology
• 7: Fine arts. Games. Shows. Sports
• 8: Language. Linguistics. Literature
• 9: Geography. Biographies. History

The numbers and notations of the CDU are ordered following the hierarchical principle that goes from the general to the particular. Each table is divided in turn into another ten groups, and so on without limit; it is a decimal rating. The notation is structured using Arabic numerals that do not function as integers.

Side tables

Coordination and extension

The coordination sign (+) joins two or more non-consecutive CDU numbers, to designate associated concepts or different aspects of the same concept for which there is no number that represents them.

Example: (470+571) Russia, both the European and Asian parts.

The extension sign (/) joins the first and last of a series of consecutive divisions to designate associated concepts or different aspects of the same concept for which there is no number that represents them.

Example: (7/8) Central and North and South America. The Americas

Relationship, subgrouping and fixing the order

The relationship sign (:) indicates the relationship between two or more topics by connecting their CDU numbers. They restrict rather than extend the connected themes.

Example: 17:7 Morals (17) in relation to art (7)

Brackets ([]) can be used for subgrouping. It is rarely used and does not have a classificatory value. They are used to clarify relationships within the notation, especially when there are more than two.

Example: [54+66] Pure and applied chemistry [622+699](485) Mining and metallurgy in Sweden

The fixed relation sign (::) is similar to a colon. It is used to indicate a relationship that cannot be changed (in: the order does not matter, in:: it does matter).

Example: 575::576.3 Cytogenetics 77.044::355 War photographs

Common auxiliaries

They apply across all tables (they are used with any number of tables in the CDU). They are structured the same as the other tables. They have several divisions:

• Independent: are used attached to any CDU table or only as if they were main numbers. They are auxiliaries of language, form, place, race and time.
  • Language =...: distinguished by being a number preceded by the equal sign (=) The only thing this assistant does is to designate the language in which the document is written.
    • Example: 61=111 Written in English. The language is indicated when necessary. It will also serve as a basis for the subdivisions of the 8 table (811 and 821)
    • Example: 663.4(493)(075)=112.5 The beer industry in Belgium written in flamenco. When a document has more than three languages it is considered multilingual. Up to three put one behind another (in ascending order)
  • Form (0...): common assistants indicate the form or presentation of documents. They are not used to indicate the matter of documents. They are normally placed behind the notation of the subject, but if desired, all documents can be grouped in the same way or presentation under the auxiliary in a suitable way, whatever the matter.Example: 54(035) Manuals (035) of chemistry '54'
  • Place (1/9): indicate the geographical area, location and other space aspect issues of a concept classified by a main number of CDUs. It is normally used behind the notation of matter.
    • Example: 354(460) Central administration '354' in Spain (460)
  • Races, peoples and nationalities (=...): indicate the nationality or ethnic aspects of a subject, represented by a main number of the CDU. Deriving from common language assistants and can serve to distinguish linguistic-cultural groups. They usually follow the main number of the CDU.
    • Example: 398(=81/=82) North American Indian Folklore
  • Time "...": indicate the date, point in time or time interval of a theme represented by a main number of the CDU. It is quoted after the main number, but in a composite index it could be intercalated at the beginning or at the end. The dates are indicated following the sequence of year-month-day between high quotes. The year is always expressed with four digits, and month and Day with two digits completing with zeros when necessary. The dates a. C. and d. C. can be indicated with the prefix (-) for the years a. C. and the sign (+) for the years d. C. Them centuries and decades can be indicated with two and three digits respectively. The intervals of several centuries, decades or years can be indicated with the initial and final figures, using the bar (/). When one of the dates is undetermined, it is represented with three points (...) If it is necessary to indicate the exact time, minute or second of an event may be indicated using the two-digit notations separated by a point (.)
    • Examples: 785.7"18" 19th-century camera music ("18")
    • "1898.12.11" 11 December 1898
    • "-0054" year 54 a. C.
    • "03" Century III
    • "1815/1830" Period from 1815 to 1830
    • 930.9".../18" History of the world until the end of the 19th century
    • "1898.12.07.15.56.03" 7 December 1898 at 3 p.m., 56 minutes and 3 seconds
• Dependent: are always used with a number of the main tables. They are viewpoint assistants, materials and people.
  • Properties -02 express general properties or attributes of entities. They are applicable in all main tables if the property aspect is secondary to the subject. They are always added as suffixes to the main number or notation that expresses the matter to qualify.
    • example: -021.181 Fantasy
    • -024.12 Synthetic
    • -028.14 Summary
  • Materials -03...: indicate the materials or components in which it is made or of which an object is composed. They are applied in all main tables when the appearance of the material is secondary. They cannot be used independently or first quoted in a composite notation. They always go after a main number. They can be indicated by replacing -03 by an apostrophe (')
    • Example: -036.674 Polyester resins
      • -037.52 Glass fiber
      • -036.674'752 Polyester and fiberglass
      • Personal persons and characteristics -05: they always indicate people or their characteristics, but they never apply to objects or disciplines. They are applicable to all main tables, if the personal aspect is secondary to the subject. Subdivisions can be combined with each other or with other assistants. They cannot be used independently or first quoted in a composite notation. They always go behind a main number or notation that expresses the subject you qualify.
      • Example: 294.3 Buddhism
      • 294.3-05 Buddhists

The order in case of appearance of all is the following: points of view, place, time, form, materials and people, language, races and peoples.

Parallel Subdivision

Its symbol looks like (≈). We must start from the number in front of the sign, and after the number that interests us in the table that goes after the sign, we find the corresponding number that indicates the auxiliary we need.

Example:

061.232 Companies formed by specific social groups 061.232≈323.3 indicates that it can be specified by going to the table of 323.3 We want the class of farm workers: 323,333

The 323.333 no longer interests us,

061.232 323.333

so the result is: 061.232.33

Specification of a subject by means of notations foreign to the CDU

• The asterisco (*): enters a notation that is not an authorized CDU number. The source of the code should be indicated in a note. It can also be used to indicate the allocation of an unauthorized notation and used only locally for a missing concept in the CDU.

Example: 523.44*433 Minor planet Eros (number authorized by the IAU) 546.42.027*90 Strontium 90 (atomic mass number of the isotope)

• Direct alphabetic specification (A/Z): for alphabetic specification alphabetic notation is added directly to the base number of the CDU without using the asterisk or leaving blank space.

Example: (492.83Utrecht) City of Utrecht

Subdivisions of special auxiliaries

The special auxiliaries subdivisions -1/-9,.01/.09 and '0/'9 are of limited application. In special auxiliaries the same notation may be used with different meanings in different parts of the main tables.

There are three types of notations for the subdivisions of special auxiliaries:

• Series with script -1/-9: they are analytics or function differentials, and serve to indicate elements, components, properties and other details of the subject matter of the main number of the CDU.
• Series with point-zero.01/.09: are used for more diverse purposes. They offer classes and subclasses of recurrent characteristics such as aspects, studies, activities, processes, facilities and equipment.
• Series with apostropho '0/'9: they have a synthesis or integrative function, indicating composite matters through composite notations. Many times they are listed completely, but in other places they derive from main numbers by parallel divisions.

Special auxiliaries can be used alone or in combination with other auxiliaries:

• Citing a single auxiliary
• Citing several auxiliaries with the same symbol (homogenous chain)
• Citing various auxiliaries with different symbols (heterogeneous chain)

Advantages and disadvantages

Advantages

• Univocity of numbers
• Possibility of system expansion
• The usefulness in ordering documents
• The main tables are of hierarchical structure, making the scheme flexible to some extent. This is an advantage not a disadvantage, the fact that it is flexible, makes that combination of numbers facilitate the thematic expansion.

Disadvantages

• Slowness to introduce any change
• The fact that it allows to combine different elements to indicate complete subjects makes the syntax complique
• Alphabetical index is very poor
• Many concepts appear by duplicate in tables
• It is an artificial code, so it can produce some rejection in the user

Differences between CDU and CDD

• The CDU has been evolving and applied more generally in continental Europe (Germany, France, Spain, Italy...), while Dewey's decimal classification (CDD) has been used mainly in Anglo-Saxon countries (Ireland, United Kingdom, United States, part of the Commonwealth of Nations) and Latin America.
• The CDU is more complex to use than the CDD, offering not only a system of subdivisions every three digits, but the possibility of combining matter with others through various symbols. It is even possible to create new categories without changing the classification by linking some figures with others. A clear example in this respect that is usually given in the faculties of biblioconomy to the students who learn to handle the CDU is the Bioethics, which is classified by relationing the digits of the Ethics (Philosophy, in class 1) with those of Biology (Health Sciences, in class 6).
• Therefore the CDU offers a system of scientific use for the organization of knowledge, while the CDD is usually linked to the classification of documents and the organization of a library.
• In the CDU there is a vacant main class (4), which is reserved for future restructurings, while the CDD employs all from 0 to 9.

TOU Management

The International Bibliographic Institute, founded by Paul Otlet, was renamed the International Federation for Documentation in 1938. The International Federation for Documentation (FID) was in charge, for years, of editing the CDU. Beginning in 1992, the rights to CDU were transferred to a consortium of publishers. The body in charge of editing the versions of the CDU in Spanish is the Spanish Association for Standardization and Certification (AENOR).

The CDU today

In Spain the CDU was known from the beginning and Manuel Castillo, for example, wrote articles about it. In 1915, some instructions were approved that determined that the CDU should be used in the new popular libraries that appeared. The director of the National Library chose the CDU to make the systematic catalog of subjects. After the Civil War, a ministerial order establishes that public libraries have to use the CDU. In 1989 its use ceased to be mandatory, but it was mandatory to carry out a systematic catalog of subjects, without specifying with what classification. The latest editions have been based on a Master Reference File where all schematic changes are reflected.

Although the CDU is an appropriate system so that the user who goes to free access generalist libraries is able to easily locate the documents that refer to a single subject, we have^[who?] Needless to say, there are large gaps in university and specialized libraries. However, this type of library continues to use the CDU for standardization and comfort criteria (cooperative cataloging and interlibrary loan would be more complicated without a common classification system).