Posted By Hermine Vermeij,
Friday, May 01, 2015
Updated: Friday, May 01, 2015
Working group members: Anne Adams, Tracey Snyder, Hermine Vermeij (group leader)
This working group was charged to examine the MARC-to-BIBFRAME transformation of music genre and form terms in bibliographic records. Despite what we considered to be rather simple MARC coding in the 655, we found that the current mapping is highly unsatisfactory. This report will outline our methodology, findings, and recommendations.
We limited our scope to MARC fields that explicitly refer to genre and/or form. Therefore, we did not examine subject headings, despite the fact that MARC 650 fields contain a large amount of music genre and form information. We are aware of separate projects spearheaded by MLA’s Vocabularies Subcommittee and Genre/Form Task Force that have the goals of creating medium of performance and genre/form fields from legacy subject headings and other data; we did not wish to try to duplicate their efforts.
Fields we studied:
655 (Index Term - Genre/Form) - The transformation of the 655 was our highest priority; this is the field in which most controlled genre/form terms will be recorded in bibliographic records, especially as use of LCGFT (Library of Congress Genre/Form Terms) increases.
008 positions 18-19 (Form of composition--”Comp” in OCLC) - Coded information from a closed list.
047 (Form of Musical Composition Code) - An expansion of the coded information in the 008, used when there are multiple forms present.
380 (Form of Work) - Generally used in the Authority Format, but occasionally found in bibliographic records.
We selected a sample of 20 OCLC records, all of which contained one or more of the fields listed above. Both notated music and performed music were represented in the sample set, as were both art music and popular music. The genre/form terms in 655s were a mix of (1) LCGFT terms that have identical counterparts in LCSH, (2) LCGFT terms that do not have precedent in LCSH, and (3) LCGFT terms that are identical to a variant term in LCSH.
Both tools attempted to map the 655 field to BIBFRAME vocabulary. LC’s tool mapped all terms in 655s to bf:Topic, which appears under “Subjects” in the tool’s user interface. This is not desirable, as the more appropriate term bf:genre is available.
Additionally, LC’s tool attempted to link the LCGFT terms to an authority record. Unfortunately, the linked authority records were incorrect in all cases. We found that the tool recognizes LCGFT as the bf:authoritySource (correct), but then links them via bf:hasAuthority to LCSH (incorrect). For example, the relevant portion of RDF XML for a record using the LCGFT term Chamber music looks like this:
The last link is to the LCSH heading Chamber music.
This result was repeated in all cases when LCGFT and LCSH strings were identical. In cases where a term from LCGFT is not also in LCSH (e.g. Parts (Music)), the tool does not link to an authority record. In the interesting case where a term from LCGFT also appears as a variant term for an LCSH term (e.g., the LCGFT term Art music, which is a variant term of Music in LCSH), the tool links to the authority record for the preferred LCSH term.
Zepheira’s tool uses different vocabulary from LC’s; the namespaces cited in their RDF results include several vocabularies from bibfra.me, which has been developed separately from LC’s BIBFRAME project. Thus, the two tools were difficult to compare.
Curiously, Zepheira’s tool mapped terms in 655s to Genre (vb:Genre, from http://bibfra.me/vocab/lite/) when we first began testing; at some point the mapping changed and it currently maps terms in 655s twice; once to Concept and once Form (both from the same vocabulary source, http://bibfra.me/vocab/lite/). We don’t know why the change was made.
Examples from the same record, run through the Zepheira tool at different times:
LC’s tool did not attempt to map the 008 positions 18-19, the 047 field, or the 380 field.
Zepheira’s tool does make an effort to map these fields, to varying degrees of success. The 008 18-19 map to ns2:formOfComposition (from http://bibfra.me/vocab/marc/), and the codes are expanded to full terms (e.g., formOfComposition "operas" for the 008 18-19 values “op”).
The 047 seems to map to a sort of placeholder; it appears as tag-047-XX-a (from http://bibfra.me/vocab/relation/), and the codes remain in their original form (e.g., ns3:tag-047-XX-a "fm", "rc").
Mapping the 655 correctly should be a high priority for BIBFRAME implementation. A successful mapping would:
Map terms to bf:genre.
Include bf:authoritySource (LC’s tool already seems to do this correctly).
Link to the correct authority using bf:hasAuthority.
The other fields we examined are of lower importance, but we still recommend they be mapped in some way to avoid data loss.
We believe the 008 18-19, the 047 $a, and the 380 $a could all be mapped to bf:genre. Expanding the codes in the 008 18-19 and the 047 to more understandable terms, as Zepheira’s tool did with the 008 18-19, would be desirable.