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Dewey Decimal Classification: Wikis


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The Dewey Decimal Classification (DDC, also called the Dewey Decimal System) is a proprietary system of library classification developed by Melvil Dewey in 1876; it has been greatly modified and expanded through 22 major revisions, the most recent in 2003.[1] This system organizes books on library shelves in a specific and repeatable order that makes it easy to find any book and return it to its proper place. The system is used in 200,000 libraries in at least 135 countries.[2][3]

A designation such as Dewey 16 refers to the 16th edition of the DDC.



The DDC attempts to organize all knowledge into ten main classes. The ten main classes are each further subdivided into ten divisions, and each division into ten sections, giving ten main classes, 100 divisions and 1000 sections. DDC's advantage in using decimals for its categories 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 at least 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 + .04 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 of the decimal number, e.g. 050, 220, 330, 330.973, 331. When two books have the same classification number the second line of the call number (usually the first letter or letters of the author's last name, the title if there is no identifiable author) is placed in alphabetical order.

It is a common misconception that all books in the DDC are non-fiction. The DDC has a number for all books, including fiction: American fiction is classified in 813. Most libraries create a separate fiction section to allow shelving in a more generalized fashion than Dewey provides for, or to avoid the space that would be taken up in the 800s.

Some parts of the classification offer options to accommodate different kinds of libraries. An important feature of the scheme is the ability to assign multiple class numbers to a bibliographical item and only use one of them for shelving. The added numbers appear in the classified subject catalog (though this is not the usual practice in North America). For the full benefit of the scheme the relative index and the tables that form part of every edition must be understood and consulted when required. The structure of the schedules is such that subjects close to each other in a dictionary catalog are dispersed in the Dewey schedules (e.g., architecture of Chicago quite separate from geography of Chicago).


Classes listed

The system is made up of ten main classes or categories, each divided into ten secondary classes or subcategories, each having ten subdivisions.

Administration and publication

While he lived, Melvil Dewey edited each edition himself: he was followed by other editors who had been very much influenced by him. The earlier editions were printed in the peculiar spelling that Dewey had devised: the number of volumes in each edition increased to two, then three and now four.

The Online Computer Library Center of Dublin, Ohio acquired the trademark and copyrights associated with the DDC when it bought Forest Press in 1988. OCLC maintains the classification system and publishes new editions of the system. The editorial staff responsible for updates is based partly at the Library of Congress and partly at OCLC. Their work is reviewed by the Decimal Classification Editorial Policy Committee (EPC), which is a ten-member international board that meets twice each year. The four-volume unabridged edition is published approximately every seven years, the most recent edition (DDC 22) in mid 2003.[4] The web edition is updated on an ongoing basis, with changes announced each month.[5]

The work of assigning a DDC number to each newly published book is performed by a division of the Library of Congress, whose recommended assignments are either accepted or rejected by the OCLC after review by an advisory board; to date all have been accepted.

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.


DDC's numbers formed the basis of the more expressive but complex Universal Decimal Classification (UDC), which combines the basic Dewey numbers with selected punctuation marks (comma, colon, parentheses, etc.). Adaptations of DDC for specific regions outside the English-speaking world include the Korean Decimal Classification, the New Classification Scheme for Chinese Libraries and the Nippon Decimal Classification (Japanese).

Comparison with Library of Congress Classification

Besides its frequent revision, DDC's main advantage over its chief American rival, the Library of Congress Classification system developed shortly afterward, is its simplicity. Thanks to the use of pure notation, a mnemonics system and a hierarchical decimal place system, it is generally easier to use.[citation needed]

DDC and UDC are more flexible than Library of Congress Classification because of greater use of facets (via auxiliary tables) while Library of Congress Classification is almost totally enumerative.

DDC's decimal system means that it is less hospitable to the addition of new subjects, as opposed to Library of Congress Classification, which has 21 classes at the top level. DDC notations can be much longer compared to other classification systems.

Another disadvantage of DDC is that it was developed in the 19th century essentially by one man and was built on a top-down approach to classify all human knowledge, which makes it difficult to adapt to changing fields of knowledge. The Library of Congress Classification system was developed based mainly on the idea of literary warrant; classes were added (by individual experts in each area) only when needed for works owned by the Library of Congress. As a result, while the Library of Congress Classification system was able to incorporate changes and additions of new branches of knowledge, particularly in the fields of engineering and computer science (the greater hospitability of the Library of Congress Classification was also a factor), DDC has been criticized for being inadequate in covering those areas. It is asserted that, as a result, most major academic libraries in the US do not use the DDC because the classification of works in those areas is not specific enough, although there are other reasons that may truly be more weighty, such as the much lower expense of using a unique "pre-packaged" catalog number instead of having highly skilled staff members engaging in the time-consuming development of catalog numbers.

The Library of Congress Classification system is not without problems. Because each area is developed by an expert according to demands of cataloging, there is little consistency. It is also highly US-centric (more so than DDC) because of the nature of the system, and it has been translated into far fewer languages than DDC and UDC.

In Pop culture


  1. ^ DDC 22 Print Edition
  2. ^ "Dewey Services". Online Computer Library Center. 2009. Retrieved 2009-11-04. "Offers library users familiarity and consistency of a time-honored classification system used in 200,000 libraries worldwide" 
  3. ^ "Countries with libraries that use the DDC". Online Computer Library Center. 2009. Retrieved 2009-11-04. "Libraries in more than 135 countries use the Dewey Decimal Classification (DDC) system to organize their collections for their users. [Only 135 countries are actually listed.]" 
  4. ^ Latest versions - OCLC - Dewey Services
  5. ^ Updates - OCLC - Dewey Services
  6. ^

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Up to date as of January 14, 2010

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