Bibliographic control in the context of Machine-readable form

A bibliographic record is an entry in a bibliographic index (or a library catalog) which represents and describes a specific resource. A bibliographic record contains the data elements necessary to help users identify and retrieve that resource, as well as additional supporting information, presented in a formalized bibliographic format. Additional information may support particular database functions such as search, or browse (e.g., by keywords), or may provide fuller presentation of the content item (e.g., the article's abstract).

Bibliographic records are usually retrievable from bibliographic indexes (e.g., contemporary bibliographic databases) by author, title, index term, or keyword. Bibliographic records can also be referred to as surrogate records or metadata. Bibliographic records can represent a wide variety of published contents, including traditional paper, digitized, or born-digital publications. The process of creation, exchange, and preservation of bibliographic records are parts of a larger process, called bibliographic control.

In information science, authority control is a process that organizes information, for example in library catalogs, by using a single, distinct spelling of a name (heading) or an identifier (generally persistent and alphanumeric) for each topic or concept. The word authority in authority control derives from the idea that the names of people, places, things, and concepts are authorized, i.e., they are established in one particular form. These one-of-a-kind headings or identifiers are applied consistently throughout catalogs which make use of the respective authority file, and are applied for other methods of organizing data such as linkages and cross references. Each controlled entry is described in an authority record in terms of its scope and usage, and this organization helps the library staff maintain the catalog and make it user-friendly for researchers.

Catalogers assign each subject—such as author, topic, series, or corporation—a particular unique identifier or heading term which is then used consistently, uniquely, and unambiguously for all references to that same subject, which removes variations from different spellings, transliterations, pen names, or aliases. The unique header can guide users to all relevant information including related or collocated subjects. Authority records can be combined into a database and called an authority file, and maintaining and updating these files as well as "logical linkages" to other files within them is the work of librarians and other information catalogers. Accordingly, authority control is an example of controlled vocabulary and of bibliographic control.

In information retrieval, an index term (also known as subject term, subject heading, descriptor, or keyword) is a term that captures the essence of the topic of a document. Index terms make up a controlled vocabulary for use in bibliographic records. They are an integral part of bibliographic control, which is the function by which libraries collect, organize and disseminate documents. They are used as keywords to retrieve documents in an information system, for instance, a catalog or a search engine. A popular form of keywords on the web are tags, which are directly visible and can be assigned by non-experts. Index terms can consist of a word, phrase, or alphanumerical term. They are created by analyzing the document either manually with subject indexing or automatically with automatic indexing or more sophisticated methods of keyword extraction. Index terms can either come from a controlled vocabulary or be freely assigned.

The term "descriptor" was by Calvin Mooers in 1948. It is in particular used about a preferred term from a thesaurus.