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Library Automation

Notes The structure of MARC records is an implementation of national and international
standards, e.g., Information Interchange Format (ANSI Z39.2) and Format for Information
Exchange (ISO 2709).
Content designation, the codes and conventions established to identify explicitly and
characterize further the data elements within a record and to support the manipulation of
those data, is defined in the MARC 21 formats.
The content of most data elements is defined by standards outside the formats, e.g.,
Anglo-American Cataloguing Rules, Library of Congress Subject Headings, National
Library of Medicine Classification. The content of other data elements, e.g., coded data
section 9 below), is defined in the MARC 21 formats.
A MARC 21 format is a set of codes and content designators defined for encoding machine-
readable records. Formats are defined for five types of data: bibliographic, holdings, authority,
classification, and community information.
MARC 21 Format for Bibliographic Data contains format specifications for encoding data
elements needed to describe, retrieve, and control various forms of bibliographic material.
The MARC 21 Format for Bibliographic Data is an integrated format defined for the
identification and description of different forms of bibliographic material. MARC 21
specifications are defined for books, serials, computer files, maps, music, visual materials,
and mixed material. With the full integration of the previously discrete bibliographic
formats, consistent definition and usage are maintained for different forms of material.

MARC 21 Format for Holdings Data contains format specifications for encoding data
elements pertinent to holdings and location data for all forms of material.
MARC 21 Format for Authority Data contains format specifications for encoding data
elements that identify or control the content and content designation of those portions of
a bibliographic record that may be subject to authority control.

MARC 21 Format for Classification Data contains format specifications for encoding data
elements related to classification numbers and the captions associated with them.
Classification records are used for the maintenance and development of classification
schemes.
MARC 21 Format for Community Information provides format specifications for records
containing information about events, programs, services, etc. so that this information can
be integrated into the same public access catalogues as data in other record types.
The MARC 21 formats are maintained by the Library of Congress in consultation with various
user communities.
Through maintenance and revision, content designation is added to and existing content
designation is made obsolete or deleted from formats. Content designation is made obsolete
when it is found to be no longer appropriate or when the data element involved is no
longer needed. An obsolete content designator may continue to appear in records created
prior to the date it was made obsolete. Obsolete content designators are not used in new
records. A deleted content designator is one that had been reserved in MARC 21 but had
not been defined or one that had been defined but it is known with near certainty that it
had not been used.
The principles stated in this document have developed over time. The formats contain
exceptions to the principles due to early format development decisions. While many
exceptions have been made obsolete, others remain because of the need to maintain
upward compatibility of the formats in current development.

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