Catalogs

A catalog is a structured listing of items within a collection or database, intended to help locate, identify, and access those items. A catalog can refer to a physical card file or a digital index, and a catalog record describes a single item and is stored in a catalog database.

Common forms include library catalogs (bibliographic catalogs of holdings), union catalogs (shared catalogs across libraries), product catalogs (retail formats with item descriptions and SKUs), data catalogs (metadata about datasets), and museum or archival catalogs (descriptions of objects or records). Digital catalogs may include discovery layers that provide access to multiple collections.

Core components are metadata fields such as title, creator, date, identifiers, location, and access points; subject headings and authority records help standardize terms. Standards include MARC and MODS in libraries, Dublin Core for general metadata, and ISO 25964 for library vocabularies. Cataloging rules guide description and access, with historical use of AACR2 and current practice centered on RDA.

Organization and access methods vary: arrangement can be alphabetical, hierarchical, or by subject, and many catalogs support facet navigation, search filters, and linked authority records. Data models range from relational databases to search indexes; in libraries, bibliographic databases and discovery systems are common. Data quality relies on authority control and consistent vocabularies.

History and evolution reflect a shift from handwritten card catalogs to online catalogs and web-based discovery tools. Automation has improved updating, accuracy, and interlibrary sharing, while initiatives such as BIBFRAME promote linked data to enable interoperability with other catalogs and datasets.

Functionally, catalogs support inventory management, item location, and retrieval, and underpin collection development, circulation, and interoperability across institutions. In commerce, catalogs facilitate product discovery and purchasing.