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The Library of Congress > Cataloging, Acquisitions > PCC > PCC Task Group on URIs in MARC


Although the cataloging community’s attention has largely been focused in recent times on formats for native linked data production, particularly BIBFRAME, library catalog data produced in our existing systems is already being exposed on a large scale as linked data.

Globally unique identifiers, given in the form of URIs, are a key requirement for the effective dissemination of data on the Semantic Web. Traditional library cataloging practices have not favored the explicit provision of identifiers and this has been an obstacle to the library community’s ability to exploit linked data technologies. In recent years the MARC format has been extended to provide for identifiers for a wide range of entities represented in bibliographic and authority records, but thus far these new elements have not consistently been populated. Moreover, the current practice is generally to supply an alphanumeric string rather than a URI even though URIs are available in many cases.

The cataloging community has an excellent opportunity, however, to close this gap. Any access point that is associated with an authority can readily be associated with an identifier. In addition, efforts have been under way by OCLC, among others, to create identifiers for a range of entities and reconcile MARC descriptions with them. There is therefore a great deal that libraries can do in our current environment to begin the transition from string-based descriptive and authority data. Indeed, the provision of such identifiers is already well established in some communities. In addition to enhancing the value of MARC data in the current environment, the provision of identifiers will also greatly facilitate migration to other metadata formats, including MODS and BIBFRAME.

The PCC is committed through its strategic plan to lead the transition to optimize library data for the web. Providing URIs in MARC records will greatly facilitate the reuse of MARC data as linked data and opens the way for catalogers to work with entity registries and controlled vocabularies from the larger metadata community. The time is right for PCC to develop a strategy that supports these objectives, outlined in the PCC Strategic Directions, 2015-2017.

Reporting to the PCC Policy Committee, the PCC Task Group on URIs in MARC is charged to:

  1. Identify and address any immediate policy issues surrounding the use of identifiers in MARC records that should be resolved before implementation proceeds on a large scale. These issues may include:
    • whether to use alphanumerical identifiers or URIs;
    • the use of multiple identifiers for the same entity;
    • where to put work and expression identifiers.
  2. In collaboration with the PCC Standing Committees, develop guidelines for including identifiers in MARC bibliographic and authority records.
  3. Develop a work plan for the implementation of identifiers in $0 and other fields/subfields in member catalogs and in PCC-affiliated utilities. Tasks may include:
    • determine the entities for which identifiers should be provided in an initial implementation;
    • identify source vocabularies that will need to be accommodated;
    • identify automated methods for populating and maintaining new and existing records with identifiers;
    • develop requirements for tools that will allow catalogers to work accurately and efficiently with linked data vocabularies;
    • identify functionality that will be required for library systems (including ILSs and utilities) to exchange, control, protect and update data based on identifiers;
    • develop a pilot project and identify partners.
  4. In consultation with the MARC Advisory Committee, technologists versed in linked data best practices, and other stakeholders, identify and prioritize any remaining issues concerning support for identifiers in the MARC format, and initiate MARC proposals as appropriate. Prioritization of issues should take into account impact, feasibility, and the late stage of MARC’s life cycle. Issues may include:
    • accommodating entities and relationships not currently well provisioned for identifiers in MARC;
    • consistency of provisions across MARC fields;
    • addressing distinction of URIs pointing to real world objects vs URIs pointing to documents/authorities.

    The Task Group should give priority to actions that will lead to tangible results during the lifetime of the PCC Strategic Directions, 2015-2017 (PDF; 157KB). The group should feel free to form subgroups and call on additional expertise as needed.

  5. At minimum, the group will provide status updates to the PCC Policy Committee by October 15 and April 15 each year it is in place. The Task Group is appointed for an initial term to end October 1, 2016, with the understanding that the charge and duration of the group may need to be extended or revised, depending on progress made over the coming year.




PCC URI Survey: Enhancing MARC Records with RDF URIs and Other Identifiers

  • Survey deadline: September 15, 2017

MARC proposals approved:

  • 2019-03: Defining Subfields $0 and $1 to Capture URIs in Field 024 of the MARC 21 Authority Format
  • 2019-02: Defining Source for Names and Titles in the MARC 21 Bibliographic Format
  • 2017-09: Defining Field 758 (Resource Identifier) in the MARC 21 Bibliographic Format
  • 2017-08: Use of Subfields $0 and $1 to Capture Uniform Resource Identifiers (URIs) in the MARC 21 Formats
  • 2017-01: Redefining Subfield $4 to Encompass URIs for Relationships in the MARC 21 Authority and Bibliographic Formats

MARC discussion papers converted to proposals and approved:

  • 2016-DP19: Adding Subfield $0 to Fields 257 and 377 in the MARC 21 Bibliographic Format and Field 377 in the MARC 21 Authority Format
  • 2016-DP18: Redefining Subfield $0 to Remove the Use of Parenthetical Prefix "(uri)" in the MARC 21 Authority, Bibliographic, and Holdings Formats

Task Group Chair:

  • Jackie Shieh (George Washington University), 2015-2017
  • Chew Chiat Naun (Harvard University), 2017-2018

Members and stakeholder institutions:

  • Ian Bigelow (University of Alberta)
  • Robert Bremer (OCLC)
  • Michelle Durocher (PCC Policy Committee Representative)
  • Nancy Fallgren (NLM)
  • Steven Folsom (Cornell University)
  • Paul Frank (Library of Congress)
  • Jean Godby (OCLC Research) to December 2017
  • Les Hawkins (CONSER Representative)
  • Chew Chiat Naun (PCC Standing Committee on Standards)


  • John Chapman (OCLC)
  • Galen Charlton (Evergreen)
  • Corine Deliot (British Library, consultant, ISNI specialist)
  • Reinhold Heuvelmann (German National Library (DNB))
  • Nancy Lorimer (Stanford, LD4P)
  • Terry Reese (Ohio State, MarcEdit)
  • Adam Schiff (University of Washington)
  • Jackie Shieh (George Washington University)
  • Gary Strawn (PCC Standing Committee on Applications)
  • Nate Trail (Network Development and MARC Standards Office (NDMSO), Library of Congress)
  • Melanie Wacker (Columbia, MODS)
  • Thurstan Young (British Library, MAC liaison)
  • Lihong Zhu (Washington State University, IGeLU LOD SIWG)