Universal Decimal Classification (UDC)
Universal Decimal Classification scheme was adapted by Paul Otlet and Henri La Fontaine from the Dewey Decimal Classification (DDC) [link to page on DDC] scheme and was first published (in French) from 1904 to 1907. Since then it has been extensively revised and developed.
The Classification is now owned by the UDC Consortium (UDCC); the consortium members are the International Federation for Information and Documentation (FID) which was set up to manage UDC around 1900, together with the publishers of the Dutch, English, French, Japanese and Spanish editions. One of its first actions was to create an international database which could be the source of many kinds of UDC edition. Known as the Master Reference File (MRF), the database is held at the Royal Library in the Hague and updated once a year. An Editor in Chief and an Advisory Board with international membership oversees the content of UDC and contribute to its revision.
UDC uses the same hierarchical structure with decimal notation as DDC. The more detailed the subdivision, the longer the number that represents it. However, it makes more use of number building techniques to construct numbers. There are two kinds of table in UDC. The main tables contain the hierarchical division of subjects into 10 classes that are further sub-divided. The auxiliary tables and auxiliary signs enable number building. The signs (e.g. the plus, the stroke, the colon) are used to link two (or more) numbers, so expressing relations of various kinds between two (or more) subjects. The tables list characteristics that are applicable to a range of subjects; for example place, language of text and physical form of document. There are also special auxiliaries which are only applicable in certain sections of the main tables.