Union catalog
A union catalog is a combined library catalog
Library catalog
A library catalog is a register of all bibliographic items found in a library or group of libraries, such as a network of libraries at several locations...

 describing the collections of a number of 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...

. Union catalogs have been created in a range of media, including book
A book is a set or collection of written, printed, illustrated, or blank sheets, made of hot lava, paper, parchment, or other materials, usually fastened together to hinge at one side. A single sheet within a book is called a leaf or leaflet, and each side of a leaf is called a page...

 format, microform
Microforms are any forms, either films or paper, containing microreproductions of documents for transmission, storage, reading, and printing. Microform images are commonly reduced to about one twenty-fifth of the original document size...

, cards and more recently, networked electronic databases. Print union catalogs are typically arranged by title, author or subject (often employing a controlled vocabulary
Controlled vocabulary
Controlled vocabularies provide a way to organize knowledge for subsequent retrieval. They are used in subject indexing schemes, subject headings, thesauri, taxonomies and other form of knowledge organization systems...

); electronic versions typically support keyword and Boolean
Boolean logic
Boolean algebra is a logical calculus of truth values, developed by George Boole in the 1840s. It resembles the algebra of real numbers, but with the numeric operations of multiplication xy, addition x + y, and negation −x replaced by the respective logical operations of...


Union catalogs are useful to librarian
A librarian is an information professional trained in library and information science, which is the organization and management of information services or materials for those with information needs...

s, as they assist in locating and requesting materials from other libraries through interlibrary loan
Interlibrary loan
Interlibrary loan is a service whereby a user of one library can borrow books or receive photocopies of documents that are owned by another library...

 service. They also allow researchers to search through collections to which they would not otherwise have access, such as manuscript
A manuscript or handwrite is written information that has been manually created by someone or some people, such as a hand-written letter, as opposed to being printed or reproduced some other way...


The largest print union catalog ever published is the American National Union Catalog Pre-1956 Imprints
National Union Catalog
The National Union Catalog is a printed catalog of books catalogued by the Library of Congress and other American and Canadian libraries, issued serially beginning in the 1950s. It is not related to the National Union Catalog of Manuscript Collections...

(NUC), completed in 1981. This achievement has since been superseded by the creation of union catalogs in the form of giant electronic databases, of which the largest is OCLC's WorldCat
WorldCat is a union catalog which itemizes the collections of 72,000 libraries in 170 countries and territories which participate in the Online Computer Library Center global cooperative...

. Another example is Copac
Copac is a union catalogue which provides free access to the merged online catalogues of many major university research libraries in the United Kingdom and Ireland, plus an increasing number of specialist libraries and the British Library, the National Library of Scotland and the National Library...

 provided by Research Libraries UK. A third example is Amicus, provided by Library and Archives Canada
Library and Archives Canada
Library and Archives Canada is a national memory institution dedicated to providing the best possible account of Canadian life through acquiring, preserving and making Canada's documentary heritage accessible for use in the 21st century and beyond...

The source of this article is wikipedia, the free encyclopedia.  The text of this article is licensed under the GFDL.