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DATE: December 13, 2016

NAME: Defining Field 758 (Related Work Identifier) in the MARC 21 Authority and Bibliographic Formats

SOURCE: PCC Task Group on URIs in MARC, Program for Cooperative Cataloging (PCC)

SUMMARY: This is a discussion of the possibility of defining a field 758 in the MARC 21 Authority and Bibliographic formats to identify related works.

KEYWORDS: Field 758 (AD, BD); Related Work Identifier (AD, BD)

RELATED: 2017-DP01; 2017-01

12/13/16 – Made available to the MARC community for discussion.

01/21/17 – Results of MARC Advisory Committee discussion: There was general support for the paper returning as a proposal. The committee agreed that a definition should be submitted for field 758 and not only a label. PCC should consider whether definition of field 758 is only appropriate in the Authority format. It may be useful if PCC were to carry out an analysis of the differences in how 7XX fields are defined in the Authority as opposed to Bibliographic format. It was suggested that subfield $2 may be a useful addition to field 758; subfield $a might be sufficient to provide an abbreviated reference without the requirement for $t. Additional feedback recommended that a different label for the field should be considered which dispenses with the term “related”; an alternative label might be “Corresponding Entity Identifier”. Consideration should also be given to recording expression as well as work level identifiers in field 758.

Discussion Paper No. 2017-DP02 : Defining Field 758 (Related Work Identifier)


MARC has an array of fields in the Authority and Bibliographic formats to represent related entities. This discussion paper was motivated by a specific use case not well catered for by existing provisions in MARC. This is the case where a work identifier (or URI) is available, but is not explicitly associated with an authorized access point or other title construction. Examples include a URI for an algorithmically generated entity such as an OCLC work, or a URI pointing to an external non-library source such as a Wikidata entry. For the Bibliographic format, this proposal addresses the use case where the work referenced by an identifier of this kind stands in a primary relationship with the entity described by the bibliographic record.

This need can be met by defining a new 758 field as follows:

*See PCC URI 2017-DP01 $0/$1 Discussion paper

**See British Library Proposal 2017-01  concerning redefinition of $4 to accommodate URIs. This proposal has been drafted in consultation with the PCC Task Group on URIs in MARC.


2.1. Bibliographic Format

Two existing options in the Bibliographic format were considered for the purpose outlined above:  7XX (Added Entry) and 787 (Other Relationship Entry).  However, both have characteristics reflecting legacy usage that make them problematical for representing work identifiers not associated with a preferred label.

The 700, 710, 711, 730, and 740 fields, when used in conjunction with titles, are defined in terms of the entry element. This is problematic in a linked data context where the type of entity is determined independently of the label. Thus a URI for, say, Shakespeare’s Hamlet may equally be associated with the preferred label “Shakespeare, William, 1564-1616. Hamlet” or “Hamlet (Shakespeare)”. From a linked data standpoint the array of MARC related resource fields adds unnecessary complexity, and hampers the ability of MARC to support use cases where the construction of the label is immaterial. These include implementations where no single label is preferred; where the label does not conform to the library’s preferred content standard; or where the label is not stored in the MARC record at all and is thus not immediately available to the application. In all of these cases the critical data element identifying the entity is given in $0.

Field 740 presents an interesting case. It designates a title not corresponding to an authorized form - but it also does not envisage the work in question having the status of a registered entity, and lacks provision for $0. Field 758, by contrast, does not require a heading in a prescribed form but insists that the work is identifiable through $0.

Defining field 758 as proposed has another important advantage. It bypasses the need to accommodate a work identifier in the 130 uniform title or 1XX/240 author-title field that is not directly derived from the authority for the access point found there. This is important because 1XX is non-repeatable and, under current practice, would normally be preferred for the authorized access point constructed according to the prevailing content standard (such as RDA) rather than an algorithmically generated identifier or one from an external registry or authority file.

Field 787 (Other Relationship Entry) was also considered for this purpose. However, 787 is part of the 76X-78X Linking Entry Fields block, which differs semantically from fields in the 7XX block. They may contain instance- or manifestation-level data such as publication information ($d). In traditional MARC practice they are not associated with authority records and are therefore not provisioned with $0 (although they are furnished with a $o which is currently defined to represent “other item identifier” and $w for record control number).  Using the 787 to record the work identifier (or URI) would involve either reviewing the subfielding provisions for the 76X-78X Linking Entry Fields as a whole or else accepting that 787 would be anomalous within that block.

2.2. Authority Format

The MARC Authority format provides for what may broadly be called mapping relationships in its 7XX block. They may include, according to the definition and scope statement, “Equivalent names in a multilingual thesaurus” or “Equivalent topical term headings in different authority systems”. When a MARC authority represents a work, authority 7XX could be used to denote equivalent works or expressions as represented in an alternative vocabulary or registry, such as an external authority file or a wikipedia entry for the same work.  In this paper we have proposed accommodating identifiers or URIs from such sources in the 758 field of bibliographic records. Defining authority 758 would allow the Authority format to cover a similar use case for authority records. It would fulfill a purpose similar to the one field 024 does for legacy identifiers, but would provide additional capabilities such as the ability to record the provenance of an assertion in $5, should such a practice come to be seen as desirable. Preferring 758 for URIs would, in addition, make it easier to reserve 024 for legacy identifiers.

Should the British Library’s Proposal 2017-01  find acceptance, the availability of $4 to accommodate predicate URIs would significantly extend the ability of authority 7XX to represent mapping relationships. For example, it could be used to assert specific predicates such as skos:exactMatch, skos:closeMatch, schema:sameAs, or owl:sameAs. These predicates play a central role in aligning linked data ontologies on the Semantic Web and the ability to support them would represent a considerable advance in the capabilities of the MARC Authority format. Field 758 would be well suited to use in this context since the emphasis will typically be on giving the mapping predicate and object identifier rather than the preferred label from the external vocabulary.


Bibliographic Format

1) Field 758 with authority control number, no label given:

245 10 $a Harry Potter and the Order of the Phoenix / $c J.K. Rowling.
250 ## $a Large print edition.
758 ## $0(viaf)270596747 

2) Field 758 with URI, no label given:

245 10 $a Harry Potter and the Order of the Phoenix / $c J.K. Rowling.
250 ## $a Large print edition.
758 ## $0

3) Field 758 with URI, label given:

245 10 $a Harry Potter and the Order of the Phoenix / $c J.K. Rowling.
250 ## $a Large print edition.
758 ## $t Harry Potter and the Order of the Phoenix $0

Authority format

4) Field 758

010 ## $a n  81118721
100 1# $a Beethoven, Ludwig van, $d 1770-1827. $t Symphonies, $n no. 3, op. 55, $r E♭ major
758 ## $0

5) Field 758 with mapping predicates given in $4:

010 ## $a n  81118721
100 1# $a Beethoven, Ludwig van, $d 1770-1827. $t Symphonies, $n no. 3, op. 55, $r E♭ major
758 ## $4 $0
758 ## $4 $0 $5 NIC

(Example 5 above shows that Beethoven’s Symphony no. 3 as represented in the NACO authority file has been identified via an owl:sameAs assertion with equivalent entity representations in VIAF and Wikidata. In the second occurrence of 758 Cornell University has been identified in $5 as the source of the assertion. As stated above, inclusion of URIs in $4 is contingent on acceptance of the British Library’s case for doing so.)


Recording the URI for a related work or instance in the MARC record for the resource described makes the URI available for inclusion in an RDF statement as the object when the MARC record is transformed into a linked data representation.


5.1. Does field 758 address the use case for catering for work identifiers or URIs not associated with a preferred label?

5.2. Does this discussion paper sufficiently make the case for a new field over reuse, augmentation, or redefinition of an existing field such as 730 or 787?

5.3. Can this definition be applied equally to both Authority and Bibliographic formats?

5.4. Does Authority field 758 go usefully beyond Authority field 024 (Other Standard Identifier) in its capabilities for representing alternative schemes or entity registries?

5.5. Are the subfields proposed the ones needed for field 758 to meet the use cases described?

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