OCLC also runs WorldCat, name of the OCLC Online Union Catalog, which is a merged electronic catalog of libraries around the world, and probably the world's largest bibliographic database with its 38 million records (at the beginning of 1998) in 400 languages (with transliteration for non-Roman languages), and an annual increase of 2 million bibliographic records.
WorldCat is derived from a concept which is the same for all union catalogs: earn time to avoid the cataloguing of the same document by many catalogers worldwide. When they are about to catalog a publication, the catalogers of the member libraries search the OCLC catalog. If they find the corresponding record, they copy it in their own catalog and add some local information. If they don't find the record, they create it in the OCLC catalog, and this new record will immediately be available to all the catalogers of the member libraries worldwide.
Unlike RLIN, another international bibliographic database (see below) which accepts several records for the same document, the OCLC Online Union Catalog takes into consideration only one record per document, and emphatically requests its members not to create double records for documents which have already been cataloged. The records are created in USMARC format (MARC: machine readable catalog) according to the Anglo-American Cataloguing Rules, 2nd version (AACR2).
What is the history of OCLC? According to the website:
"In 1967, the presidents of the colleges and universities in the state of Ohio founded the Ohio College Library Center (OCLC) to develop a computerized system in which the libraries of Ohio academic institutions could share resources and reduce costs.
OCLC's first offices were in the Main Library on the campus of the Ohio State University (OSU), and its first computer room was housed in the OSU Research Center. It was from these academic roots that Frederick G. Kilgour, OCLC's first president, oversaw the growth of OCLC from a regional computer system for 54 Ohio colleges into an international network. In 1977, the Ohio members of OCLC adopted changes in the governance structure that enabled libraries outside Ohio to become members and participate in the election of the Board of Trustees; the Ohio College Library Center became OCLC, Inc. In 1981, the legal name of the corporation became OCLC Online Computer Library Center, Inc. Today, OCLC serves more than 27,000 libraries of all types in the U.S. and 64 other countries and territories."
Both complementary and different from the OCLC Online Catalog (WordCat) with its 38 million records (with one record per document), the Research Libraries Information Network (RLIN) includes 88 million records (with several records per document).
RLIN is run by by the Research Libraries Group (RLG). The central RLIN database is a union catalog of nearly 88 million items held in comprehensive research libraries and special libraries in RLG member institutions, plus over 100 additional law, technical, and corporate libraries using RLIN. It includes:
a) Records that describe works cataloged by the Library of Congress, the National Library of Medicine, the U.S. Government Printing Office, CONSER (Conversion of Serials Project), The British Library, the British National Bibliography, the National Union Catalog of Manuscript Collections, and RLG's members and users;
b) Comprehensive representation of books cataloged since 1968 and rapidly expanding coverage for older materials;