Other standards work in conjunction with MARC, for example, Anglo-American Cataloguing Rules (AACR)/Resource Description and Access (RDA) provide guidelines on formulating bibliographic data into the MARC record structure, while the International Standard Bibliographic Description (ISBD) provides guidelines for displaying MARC records in a standard, human-readable form.
Since it was first developed at a time when computing power was low, and space precious, MARC uses a simple three-digit numeric code (from 001-999) to identify each field in the record.
Libraries typically expose their records as MARCXML via a web service, often following the SRU or OAI-PMH standards.
Resource Description and Access, for example, defines how the physical characteristics of books and other items should be expressed.
MARC 21 is based on the NISO/ANSI standard Z39.2, which allows users of different software products to communicate with each other and to exchange data.
MARC-8 is based on ISO 2022 and allows the use of Hebrew, Cyrillic, Arabic, Greek, and East Asian scripts.
[5] MARCXML was developed by the Library of Congress and adopted by it and others as a means of facilitating the sharing of, and networked access to, bibliographic information.
The MARCXML primary design goals included:[6] The future of the MARC formats is a matter of some debate among libraries.
The Library of Congress has launched the Bibliographic Framework Initiative (BIBFRAME),[7] which aims at providing a replacement for MARC that provides greater granularity and easier re-use of the data expressed in multiple catalogs.