Dewey Decimal Classification

From Wikipedia, the free encyclopedia

For the similar-sounding numeral system see duodecimal system.

The Dewey Decimal Classification (DDC, also called the Dewey Decimal System) is a proprietary system of library classification developed by Melvil Dewey in 1876, and since greatly modified and expanded in the course of the twenty-two major revisions, the most recent in 2004.

1 How it works
2 DDC compared to other classification systems
3 Ownership
4 Classes
5 See also
6 External links

[edit] How it works

The DDC attempts to organize all knowledge into ten main classes that, excluding the first class (000 Computers, information and general reference), are meant to proceed from the divine (philosophy and religion) to the mundane (history and geography).

The ten main classes are then further subdivided. Each main class has ten divisions and each division has ten sections. Hence the system can be neatly summarized in 10 main classes, 100 divisions and 1000 sections. DDC's cleverness is in choosing decimals for its categories; this allows it to be both purely numerical and infinitely hierarchical.

It also uses some aspects of a faceted classification scheme, combining elements from different parts of the structure to construct a number representing the subject content (often combining two subject elements with linking numbers and geographical and temporal elements) and form of an item rather than drawing upon a list containing each class and its meaning.

Except for general works and fiction, works are classified principally by subject, with extensions for subject relationships, place, time or type of material, producing classification numbers of not less than three digits but otherwise of indeterminate length with a decimal point before the fourth digit, where present (e.g. 330 for economics + 9 for geographic treatment + 4 for Europe = 330.94 European economy; 973 for United States + 05 form division for periodicals = 973.05, periodicals concerning the United States generally).

Books are placed on the shelf in increasing numerical order; the whole number to the left of the decimal is in counting order, while the digits to the right of the decimal are compared one digit at a time, with a blank coming before zero. (Example: 050, 220, 330.973, 331 etc.) When two books have the same subject, and therefore the same classification number, the second line of the call number, which usually has the first letter or first several letters of the author's last name (or the title if there is no identifiable author), are placed in alphabetical order.

It is a common misconception that all books in the DDC are non-fiction. However, the DDC has a number for all books, including those that generally become their own section of fiction. If DDC rules are strictly followed, American fiction is classified in 813. Most libraries create a separate fiction section because of the space that would be taken up in the 800s.

[edit] DDC compared to other classification systems

For more details on this topic, see Comparison of Dewey and Library of Congress subject classification.

DDC's numbers formed the basis of the more expressive but complex Universal Decimal Classification, which combines the basic Dewey numbers with selected punctuation marks (comma, colon, parentheses etc.). Despite its frequent revision, DDC is widely considered theoretically inferior to other more modern systems which make freer use of alphabetical characters to produce shorter classmarks for concepts of equal complexity, though it continues to offer a more expressive format than the Library of Congress Classification developed shortly afterward.

[edit] Ownership

The Online Computer Library Center of Dublin, Ohio acquired the trademark and any copyrights associated with the Dewey Decimal System when it bought Forest Press in 1988. OCLC maintains the classification system and publishes new editions. In September 2003, the OCLC sued the Library Hotel for trademark infringement. The settlement was that the OCLC would allow the Library Hotel to use the system in its hotel and marketing. In exchange, the Hotel would acknowledge the Center's ownership of the trademark and make a donation to a nonprofit organization promoting reading and literacy among children.

[edit] Classes

The system is made up of ten main classes or categories, each divided into 10 secondary classes or subcategories, each having 10 subdivisions of its own. For a more detailed list, see List of Dewey Decimal Classes.