Amsterdam, September 6-9, 1965

The UDC is a universal classification in the sense that it covers the whole universe or domain of human activity and knowledge. Although developed from the Dewey Decimal Classification, it has been considerably modified and extended over the years, and is maintained by continual revision es an efficient system for classifying and retrieving detailed information of all kinds (in books, articles, reviews, etc.).

In its main table, the whole domain of knowledge (regarded as unity) is treated hierarchically and represented notationally by a system of decimal numbering (fractions of unity, but with the initial comma or point omitted) as ten main classes 0 to 9, each of which is further divided and subdivided decimally according to need, e.g. 7 (Arts and entertainment) into 71, 72.. to 79, and 79 (Entertainment) into 791, 792, etc., thus:

0 Generalia, fundamentals of knowledge, documentation, etc.

1 Philosophy, psychology, logic, ethics and morals

2 Theology and religion(s)

3 Social sciences, politics, economics, law, administration, welfare and education, customs and tradition

(4 - vacant for new uses, linguis/span>tics now in class 8)

5  Mathematics. Natural sciences

6 Applied sciences. Medicine. Engineering and technology

7 Arts (incl. architecture and photography). Entertainment

8 Language, linguistics and literature

9 Geography, biography and history

In separate tables are listed sets of 'auxiliaries' (decimally divided numbers with special prefixed signs), which represent concepts common to all parts of the UDC or applicable throughout a particular class or section, such as 792. The Common auxiliaries include tables for Persons -05, Place and country (1/9), Time "...", Form of document (0...) and Language = ..., the first three being especially important. Special auxiliaries, with the symbols - .. . (hyphen), . 0 ... (point-nought) and '... (apostrophe), are developed differently for the various main classes and sections, as later described for 792. Free use of these auxiliaries, and of the : (colon sign) for combining numbers to denote relations between subjects, makes the UDC - at least partially - a faceted system of great flexibility. Extensive plans for the future revision of the system include further development in this direction.

UDC 792 Theatre has just been revised (P-note 832, synopsis appended); the scheme will appear in "Extensions & Corrections to the UDC", series 5 no. 6 due out in September 1965. This is a link in the revisions of the whole class 7, of which 71 (Town & country planning), 72 (Architecture) and 796/799 (Sport) were recently revised, and a similar improvement for the special auxiliaries 7.0 is in preparation.

The main schedule of 792, i.e. 792.2/.9, gives the various types of theatrical productions - plays (speech drama), operas, revues, etc.

The special .0 auxiliaries, which follow the general pattern established at 7.0 and common to the whole class 7, are developed in some detail at 792.0, where they are adapted to suit the special needs for classification within the field of theatre. They include Scenography and aesthetics, Production technique, Theatre and stage equipment, the Theatrical profession and Types of performance and presentation. These auxiliaries, like the common auxiliaries, can be used either at 792 itself (e.g. 792.01 Aesthetics of theatre and scenography in general), or attached to any of the main divisions .2/.9 (e.g. 792.54.027.4 Musical direction of operas).

Similarly, the common auxiliaries of Time "...", Place (2/9) and Person -05 may be freely combined and added to 792 itself, or to any of its main divisions 792.2/.9 and special .0 auxiliaries, thus permitting an extremely flexible arrangement. An example of subdivision may serve as a concluding illustration: