WorldCat is a union catalog
Union catalog
A union catalog is a combined library catalog describing the collections of a number of libraries. Union catalogs have been created in a range of media, including book format, microform, cards and more recently, networked electronic databases...

 which itemizes the collections of 72,000 libraries
In a traditional sense, a library is a large collection of books, and can refer to the place in which the collection is housed. Today, the term can refer to any collection, including digital sources, resources, and services...

 in 170 countries and territories which participate in the Online Computer Library Center (OCLC) global cooperative. It is built and maintained collectively by the participating libraries.


Created in 1971, it contains more than 246 million different records pointing to over 1.77 billion physical and digital assets in more than 470 languages. It is the world's largest bibliographic
Bibliography , as a practice, is the academic study of books as physical, cultural objects; in this sense, it is also known as bibliology...

 database. OCLC makes WorldCat itself available free to libraries, but the catalog is the foundation for other fee-based OCLC services (such as resource sharing and collection management). WorldCat was founded by Fred Kilgour
Fred Kilgour
Frederick Gridley Kilgour was an American librarian and educator known as the founding director of OCLC , an international computer library network and database that changed the way people use libraries...

 in 1967.

In 2003, OCLC began the "Open WorldCat" pilot program, making abbreviated records from a subset of WorldCat available to partner Web sites and booksellers, to increase the accessibility of its member libraries’ collections. In 2006, it became possible to search WorldCat directly at its website. In 2007, WorldCat Identities began providing pages for 20 million "identities", predominantly authors and persons who are the subjects of published titles.


Eastern European and Eurasia
Eurasia is a continent or supercontinent comprising the traditional continents of Europe and Asia ; covering about 52,990,000 km2 or about 10.6% of the Earth's surface located primarily in the eastern and northern hemispheres...

n library holdings are not well-represented in the system.

WorldCat operates on a batch processing
Batch processing
Batch processing is execution of a series of programs on a computer without manual intervention.Batch jobs are set up so they can be run to completion without manual intervention, so all input data is preselected through scripts or command-line parameters...

model rather than a real-time model. That is, WorldCat records are synchronized only at intermittent intervals with the underlying library catalogs instead of real-time or even every day. WorldCat merely shows that a particular item is listed in the catalog of a library, but cannot indicate if the item has been borrowed and is therefore unavailable for access by other patrons right now. As a partial workaround, WorldCat allows participating institutions to add direct links to WorldCat to their catalog entries for a particular item, but this is not as convenient as being able to view current status for all institutions owning an item on a single Web page.

External links

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