Best Practice for MARC21 Subfields Zero and One ($0 and $1)

Owned by anneadams@fas.harvard.edu
Last updated: Dec 21, 2023
3 min read


Background

In July of 2017 Metadata Standards Working Group approved the retention of the subfield 0 (zero) in bibliographic records, as defined in the MARC 21 documentation.


$0 - Authority record control number or standard number

Subfield $0 contains the system control number of the related authority or classification record, or a standard identifier such as an International Standard Name Identifier (ISNI). These identifiers may be in the form of text or a URI. If the identifier is text, the control number or identifier is preceded by the appropriate MARC Organization code (for a related authority record) or the Standard Identifier source code (for a standard identifier scheme), enclosed in parentheses. When the identifier is given in the form of a Web retrieval protocol, e.g., HTTP URI, no preceding parenthetical is used.


Since that time, the $1 has also been approved for retention: 

$1 - Real World Object URI

Subfield $1 contains a URI that identifies an entity, sometimes referred to as a Thing, a Real World Object or RWO, whether actual or conceptual. When dereferenced, the URI points to a description of that entity. A URI that identifies a name or label for an entity is contained in $0.

OCLC practice

Because the risk of a mismatch is much lower with qualified headings, OCLC is attempting to control qualified headings containing $0. Once we begin to receive updates through Alma, we will receive the controlled headings for records that are eligible for replace/merge.  OCLC will not automatically control unqualified headings.

Alma practice

Names

Alma authority control disregards the $0 when looking at string matches of the heading itself, and does not remove or otherwise take into account the $0. Even if a heading has a $0 for a non-Library of Congress vocabulary, the heading will still link to a Library of Congress authority record if there is a match on the string value.  The $0 will persist regardless. Please note that unqualified names are at risk to be linked to an incorrect authority name. See Best Practice for Name Access Points in Alma

Subjects

Alma authority control disregards the $0 when looking at string matches of the heading itself, and does not remove or otherwise take into account the $0. Even if a heading has a $0 for a non-Library of Congress vocabulary, the heading will still link to a Library of Congress authority record if there is a match on the string value and if there is a 2nd indicator of zero).  The $0 will persist regardless.

Genres

Alma authority control disregards the $0 when looking at string matches of the heading itself, and does not remove or otherwise take into account the $0. The heading will only link to a Library of Congress authority record if the second indictor is 7 and the subfield 2 contains a code for a Library of Congress vocabulary or if the second indicator is 0. (Please note that currently, when a 655 field is coded for LCSH and matches a non-preferred term in LCGFT, Alma flips the heading to the preferred LCGFT term but does not update the coding (it should change the 2nd ind to 7 and add $$2 lcgft). Genre terms in other thesauri are not affected (aat, etc.). For further information, please see the Best Practices for Genre / Form Added Entries.

Harvard best practices

The Metadata Standards Working Group, in conjunction with ITS, makes the following recommendations with regard to this field:

  • Creation:

    • MSWG is agnostic about whether or not to add $0 or $1 in workflows.  We leave this decision up to individual units.  When adding these subfields, however, do not manually type in the links.  MSWG recommends the use of macros, text strings, or copy/paste options in order to ensure better accuracy for our patrons.

  • Retention:
    • For LC vocabularies:
      • You are not required to control these headings in Connexion, although you are free to do so if this is appropriate for your unit and workflow. If you do control these headings, it will remove the $0 subfield (any $1 will remain), which is expected.

    • For all other vocabularies:
      • Retain $0 and $1 subfields, as they will be important for linked data and other future projects (and to retain information on the correct identity in cases of incorrect flipping)


Examples in Alma



These subfield values can represent many different vocabularies, including FAST, ISNI, or other source vocabularies.  Occasionally, they may even include a subfield zero for LC vocabularies. 


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