MARC 21 Format for Authority Data: National Level Requirements (Network Development and MARC Standards Office, Library of Congress)

Introduction
Leader/Directory
Tracing Fields
00X -- Control Fields
01X-09X -- Numbers and Codes
1XX -- Headings
2XX -- Complex See Reference
3XX -- Complex See Also Reference - Subject
4XX -- See From Tracing Fields
5XX -- See Also From Tracing Fields
6XX -- Complex See and See Also References; Series Treatment; Notes
7XX -- Heading Linking Entries
8XX -- Other Variable Fields

INTRODUCTION

This document contains a list of MARC 21 authority data elements with codes showing requirements for national-level records in the United States. National-level records are required to contain sufficient information to allow them to be used by various national and world-wide agencies. The national-level record requirements presented here are not intended to prevent a cataloging agency from using any valid MARC 21 authority data element. They are provided to facilitate the standardization of the content of MARC 21 authority records.

REQUIREMENT CODES

MARC 21 authority records are represented by codes. Three different codes have been used to differentiate between data elements that must always be present, that should be present when information is available, and optional data elements. The requirement codes used in this document are defined as follows:

A - Mandatory if applicable
A data element that must be present in an authority record if it is appropriate for the heading, etc. and if the information is available. The fill character (|) is not permitted in data elements that are mandatory if applicable.

M - Mandatory
A data element that must be present in every authority record. The fill character (|) is not permitted in mandatory data elements.

O - Optional
An optional data element is not required in an authority record, but may be present if desired. The fill character (|) is permitted in the optional character positions of field 008 (Fixed-Length Data Elements) and control subfield $w character positions in the 4XX and 5XX fields.

INDICATOR POSITIONS

In MARC 21, a valid value is mandatory in both indicator positions for fields that include indicator positions. In the MARC 21 Format for Authority Datathis includes fields 010 through 8XX and any locally-defined fields within the 010 to 999 range that may be used by a cataloging agency. When an indicator position is present, but undefined a blank is always used. The fill character (|) is never used in indicator positions in MARC 21. Since indicator values are mandatory in all MARC 21 fields (except 001-008), no national-level requirements are given. If a field is present in a record, valid indicator values must be supplied. The individual field descriptions provide listings of valid indicator values.