Main class  (& Main class order)

Main classes represent the highest-level divisions of a classification system. In Dewey Decimal Classification (DDC), for example, the 10 main classes are indicated by the Arabic numerals 0-9 in the first digit of the notation:


000 - Generalities

100 - Philosophy, parapsychology and occultism, psychology

200 - Religion

300 - Social sciences

400 - Language

500 - Natural sciences and mathematics

600 - Technology (applied sciences)

700 - Arts (fine and decorative arts)

800 - Literature (belles-lettres) and rhetoric

900 - Geography, history, and auxiliary disciplines



In most library systems main classes represents scientific and scholarly disciplines, while in scientific classifications they represent objects (e.g. living objects and non-living objects), cf.  aspect classification and phenomenon class.



How are the order of the main classes determined? One answer is given by Mills & Ball:


"Bliss Bibliographic Classification (BC2) is an internationally accepted detailed general classification which is based on clear and comprehensive principles for both its overall structure (main-class order) and the internal structure of each and every class. The former is based on the theory of integrative levels first advanced by Comte. The second is based on the revolutionary theory of facetted classification developed by Ranganathan and elaborated by the CRG - (British) Classification Research Group" .  (Mills & Ball, 2007, back cover).


Other systems may be based on other principles for ordering main-classes, but mostly they are not based on any explicit principle. 


In thesauri, the corresponding concept is top term (tt), which symbolizes the highest hierarchical level in the thesaurus (whether generic or partitive relation). Example: Zealand. Broader term partitive: Denmark. TT: Geographical areas.


In classification and taxonomy theory are the ultimate classes termed categories.





Mills, J. & Ball, C. (2007). Bliss Bibliographic Classification. Class W. The Arts. München: K. G. Sauer Verlag.


Se also: Category (Epistemological lifeboat);  Generic relation; Hierarchy;




Birger Hjørland

Last edited: 19-01-2007