Bibliographic Framework Initiative (Library of Congress)

The Library of Congress > BIBFRAME > BIBFRAME 2.0 to MARC 21 Conversion Specifications

The following specifications were developed to support a pilot in the use of BIBFRAME 2.0 at the Library of Congress. They specify the conversion of BIBFRAME Work and Instance descriptions to MARC Bibliographic records. The current version is bibframe2marc v2.5.

BIBFRAME Conversion Specifications

Usage Notes

The BIBFRAME to MARC specifications are based on the MARC to BIBFRAME conversion specifications maintained by the Library of Congress and track that conversion closely. There are separate spreadsheets for the BIBFRAME Work, Instance, Admin Metadata, and Item conversions, along with a spreadsheet for the creation of the MARC 008 field. Properties, classes, URIs and text strings are listed, followed by the resulting MARC field, indicators, subfields, and any default values. In some fields, a URI in the BIBFRAME description dictates the MARC field that is output. In other, a text string determines what MARC field, indicator, or subfield is assigned. As much as possible, URIs in the BIBFRAME description are preserved in the MARC $0 field. The accompanying Process document provides explanatory specifications that apply to multiple fields in the MARC record created by the conversion program.

The specifications use the vocabularies and authorities that are in ID.LOC.GOV – Linked Data Service at -- as they are resident in the Library’s BIBFRAME descriptions.

Note that these specifications will be changed as needed as we develop the system for the BIBFRAME 2.0 Pilot. Revisions to specifications will be indicated in the file name and the URL on the document will indicate a revision (e.g., v2.3, v2.4, …).

MARC Conventions used in the Conversions

In the BIBFRAME to MARC conversion, it was occasionally necessary to make choices about the placement of data elements. In addition, the Library of Congress makes extensive use of URIs in BIBFRAME data and wished to avoid the loss of these URIs in the MARC version of a description. The following conventions were used:

  • The 008 and 007/00 and 007/01 fields are created but they are also duplicated in other fields where a URI for the value could be recorded.
  • For data elements that could have multiple locations in a MARC record, only one location was usually chosen.
  • Selected 880 fields were created to pair with the 245, 250, 264 and 490 fields. Non-Latin data will appear in non-880 fields and there is less transliteration of non-Latin data.
  • For LCSH subject headings, a URI only appears if it matches the entire heading. Complex headings that are created from free-floating subdivisions will not include URIs.
  • Punctuation at subfield boundaries is not inserted if it is not carried in the corresponding BIBFRAME element.
  • URIs are carried in the MARC $0 subfields. 

last edit: 11/29/2023