A union catalog is a combined

library catalog A library catalog (or library catalogue in British English) is a register of all bibliographic items found in a library or group of libraries, such as a network of libraries at several locations. A catalog for a group of libraries is also ...

describing the collections of a number of libraries. Union catalogs have been created in a range of media, including

book A book is a medium for recording information in the form of writing or images, typically composed of many pages (made of papyrus, parchment, vellum, or paper) bound together and protected by a cover. The technical term for this physi ...

format,

microform Microforms are scaled-down reproductions of documents, typically either films or paper, made for the purposes of transmission, storage, reading, and printing. Microform images are commonly reduced to about 4% or of the original document size. F ...

card Card or The Card may refer to: * Various types of plastic cards: **By type ***Magnetic stripe card ***Chip card ***Digital card **By function ***Payment card ****Credit card ****Debit card **** EC-card **** Identity card ****European Health Insuran ...

s and more recently, networked electronic

databases In computing, a database is an organized collection of data stored and accessed electronically. Small databases can be stored on a file system, while large databases are hosted on computer clusters or cloud storage. The design of databases s ...

. Print union catalogs are typically arranged by title, author or subject (often employing a

controlled vocabulary Control may refer to: Basic meanings Economics and business * Control (management), an element of management * Control, an element of management accounting * Comptroller (or controller), a senior financial officer in an organization * Controllin ...

); electronic versions typically support keyword and Boolean queries. Union catalogs are useful to librarians, as they assist in locating and requesting materials from other libraries through

interlibrary loan Interlibrary loan (abbreviated ILL, and sometimes called interloan, interlending, document delivery, document supply, or interlibrary services, abbreviated ILS) is a service where patrons of one library can borrow materials and receive photocopies ...

service. They also allow researchers to search through collections to which they would not otherwise have access, such as

manuscript A manuscript (abbreviated MS for singular and MSS for plural) was, traditionally, any document written by hand – or, once practical typewriters became available, typewritten – as opposed to mechanically printed or reproduced in ...

collections. The largest union catalog ever printed is the American '' National Union Catalog Pre-1956 Imprints'' (NUC), completed in 1981. This achievement has since been superseded by the creation of union catalogs in the form of electronic databases, of which the largest is

OCLC OCLC, Inc., doing business as OCLC, See also: is an American nonprofit cooperative organization "that provides shared technology services, original research, and community programs for its membership and the library community at large". It w ...

's WorldCat. Another example is

COPAC Copac (originally an acronym of Consortium of Online Public Access Catalogues) was a union catalogue which provided free access to the merged online catalogues of many major research libraries and specialist libraries in the United Kingdom and Ir ...

provided by

Research Libraries UK Research Libraries UK (RLUK) (formerly CURL) comprises 32 university libraries, 3 national libraries, and the Wellcome Collection in the United Kingdom and Ireland. Its aim is to increase the ability of research libraries to share resources amon ...

, which was superseded by Library Hub Discover in 2019. A third example is AMICUS, provided by

Library and Archives Canada Library and Archives Canada (LAC; french: Bibliothèque et Archives Canada) is the Government of Canada, federal institution, tasked with acquiring, preserving, and providing accessibility to the documentary heritage of Canada. The national arch ...

. For academic publications, several academic search engines exist to combine the

open data Open data is data that is openly accessible, exploitable, editable and shared by anyone for any purpose. Open data is licensed under an open license. The goals of the open data movement are similar to those of other "open(-source)" movemen ...

provided by

open archive An open repository or open-access repository is a digital platform that holds research output and provides free, immediate and permanent access to research results for anyone to use, download and distribute. To facilitate open access such repositor ...

s through OAI-PMH, as well as records from publishers deposited in CrossRef and other sources. They include BASE, CORE and Unpaywall, which indexes over 20 million open access publications as of 2020.

References

Library catalogues {{Library-stub