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The Dewey Decimal Classification (DDC), or Dewey Decimal System, is a proprietary library classification system created by Melvil Dewey in 1876. It has been revised and expanded through 23 major editions, the latest issued in 2011. Dewey was responsible for all revisions until his death in 1931. A designation number, such as Dewey 16 for the 16th edition, is given for each revision.
A library assigns a DDC number that unambiguously locates a particular volume to within a short length of shelving which makes it easy to find any particular book and return it to its proper place on the library shelves. The system is used in 200,000 libraries in at least 135 countries.
The DDC is a system of library classification made up of ten classes, each divided into ten divisions, each having ten sections (although there are only 99 of 100 divisions and 908 of 999 sections in total, as some are no longer in use or have not been assigned).
Just as in an alphanumeric system, the DDC is 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 the form of an item, rather than drawing upon a list containing each class and its meaning. For example, 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 catalogued in ascending numerical order; when two or more books have the same classification number, the system sub-divides the class alphabetically, by the use of a call number (usually the first letter, or letters, of the author's last name, or the title if there is no identifiable author.)
The DDC has a number for all books, including fiction. 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, or simply to allow readers to find preferred authors by alphabetical order of surname.
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 (for example, architecture of Chicago quite separate from geography of Chicago).
The system is made up of seven tables and ten main classes, each of which is divided into ten secondary classes or subcategories, each of which contain ten subdivisions.
The tables are:
The classes are:
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 (OCLC) of Dublin, Ohio, United States, 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 six years, the most recent edition (DDC 23) in mid 2011. The web edition is updated on an ongoing basis, with changes announced each month.
Linked to each full edition is the single volume abridged edition designed for libraries with 20,000 titles or fewer. Abridged 14 was published in 2004, Abridged 15 is due early 2012.
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).
|This section may contain original research. (November 2008)|
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. 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. For example, it is highly US-centric because of the nature of the system, and it has been translated into far fewer languages than DDC and UDC.