by Kirk-Evan Billet, Sophie Rondeau, and William Vanden Dries
3.3.0 Sequence: introduction
The concept of sequence as manifested in bibliographic data for music resources may be divided into two areas: 1) sequence of resource components, as when the order of individual content units is important enough to be represented in data, and 2) sequence of data elements, as when ordering or adjacency bears directly on the meaning of the data. A related concern, which, for music resources, may prove the most extensive, is the correct association of a specific element of description with the corresponding individual content unit (and only that unit).
For the sequence concept, as with other music-specific data concerns in BIBFRAME, there may be a divergence of focus regarding the conversion of existing MARC data on one hand as opposed to the creation of new data on the other. In the first case, preserving and clarifying may take precedence, while in the second case, the opportunity to look at what music cataloging could do better, not only in supporting identified user tasks but in facilitating unforeseen uses of library data, may come to the fore.
BIBFRAME AV Modeling Study, in Appendix C, outlines some of the challenges associated with complex, multi-part audiovisual materials. On audio recordings, multi-part works are often presented in a sequence of tracks or content subunits. Currently, if a user is searching for subunits, he/she may only find items where the subunits have been recorded, and may not retrieve results that include the entire work. Although this may seem to be a problem of identification, it results in missed hits when sequence of subunits within a larger content unit is not recorded. Problems also arise in situations where the user has limited information about the resource. For example, a user is looking for the infamous slow movement from Mozart’s clarinet concerto. She knows it is the second movement, but does not know the title or any other musical characteristic. There is currently no controlled method of cataloging the organizational structure of multi-movement/multi-part works, making it difficult for users to find and identify the desired musical resource when searching by structural attributes. Specific elements of description, such as medium of performance, recording dates, and durations also need to be correctly associated with individual content units, and this is something current practices don’t accommodate.
3.3.1 Music resources and sequence
Categories of resources affected by the issue of sequence include:
Commercial or non-commercial audio recordings consisting of multiple individual tracks/content units related to one another by a sequence (e.g., a sound recording featuring all of Beethoven’s symphonies arranged in chronological order, or a sound recording of Bach compositions arranged by BWV number).
Commercial or non-commercial audio recordings containing a compilation of tracks/content units (e.g., a sound recording featuring a Beethoven concerto and Schubert symphony on the same instance).
Commercial or non-commercial audiovisual resources containing individual chapters or content units related to each other through a sequence (e.g., chapters from a feature film DVD).
Commercial or non-commercial audiovisual resources containing individual chapters or tracks related to each other through a compilation of units (e.g., shorts on a compilation reel).
Print resources containing multiple content units related to one another by a sequence (e.g., score of a Schubert song cycle).
Print resources containing multiple content units (e.g., score of Italian songs by various composers, or score containing the complete chamber works of a composer).
Multi-volume print resources related to one another by a sequence (e.g., Opera omnia / Joannes Mouton; volume 43 of complete works).
3.3.2 Use cases for sequence
- A professor is looking for a radio tape talk series recorded on ¼” reel that was broadcast in four parts, once a week over four consecutive weeks. The professor wants each segment of the series to be digitized for ease of access. As well, the recording dates are especially important since she is examining the development of the musicologist who produced the series. Unfortunately, the third part is missing. The professor plans to compile the musicologist’s broadcasts in a book with accompanying audio materials consisting of excerpts from various series. She needs as much information as possible about all four parts, including their correct sequence.
The music librarian received a DVD of Der Rosenkavalier requested by a faculty member responsible for organizing a concert performance of specific arias from the opera for her students. She would like the students to be able to watch particular scenes to garner a sense of the dramatic context. To save her students from having to forward through the entire video, she has requested the chapter sequence of the DVD be recorded. The librarian wants to be able to provide a more granular level of description as requested by her patrons.
An undergraduate student is looking for a recording of Régine Crespin performing songs by Gabriel Fauré. She searches with the keywords Regine Crespin Faure and retrieves a single item entitled “The voice of France.” Crespin is on the recording, but is performing “Les nuits d’été” by Berlioz, with Sylvia McNair performing songs by Fauré. Frustrated with the catalog, the student searches YouTube instead. She had to read through a lot of content notes, and wishes the library catalog provided more precise search results.
3.3.3 Current sequence practices in MARC
Current MARC handling of sequence and sequence-related data elements falls into several categories. Sequence of content units within a resource is reflected in contents notes showing the order of performed works or tracks in audio or video resources; this ordering might include associated durations, responsibility statements, etc. Print resources such as scores may also be described in terms of the order of component units. In another category, elements of description that apply to specific content units are given without any indication of this association. Examples include coded event data, such as recording dates and places in MARC 033, medium of performance information in MARC 048 and/or 382, and durations of components coded in MARC 306. In yet another category, the association of description with content may be made, but only as part of a text string (for example, “3rd, 10th works sung in Latin; remainder sung in French”) and thus unavailable for machine processing. Examples of this type include the following elements (when applying variously to individual content units and not to the entire resource): genre/form (when recorded as a note), performers, recording session information, sung language, production credits, reissue information, edition recorded, matrix numbers, medium of performance (when recorded as a note), and issue numbers pertaining to parts.
Finally, there are cases of contextual rather than precisely defined data elements—that is, cases in which sequence or adjacency of data points has semantic or associative significance. For example, an enhanced contents note relies on adjacency of subfields for correct association of data points with content units. In the case of medium of performance, MARC 382 coding requires specific ordering of subfields in order for the correct meaning to result.
3.3.4 Functional requirements
Where sequence is concerned, the BIBFRAME functionality most crucial for users of music library data falls into two categories. For content made up of constituent units which are understood on some level in terms of the order in which they occur, this sequence must be represented. For multiple content units (within an aggregating resource) each having differing attributes known to be important for user tasks, descriptive assertions must be explicitly related to the corresponding content unit. These assertions often concern performer(s), medium of performance, or genre/form, but they may also pertain to recording date or place, edition recorded, matrix numbers, or duration. Precise association of data with content is also necessary to realize the full potential of new vocabularies for medium of performance and genre/form.
Resource description interfaces must provide functionality for the representation of these sequences and relationships. Similarly, display and retrieval applications must have access to the necessary sequence and relationship information, and it should be possible to provide the user with some control of views of this information. For MARC-to-BIBFRAME conversion of existing music library data, certain MARC cases of subfield sequence or adjacency must be accounted for in any conversion process.
3.3.5 Missing parts in sequence structures
When modeling and serializing works and instances, BIBFRAME must be capable of dealing with situations in which parts of an instance are known to exist elsewhere or have existed in the past, but are missing from the resource in hand. One such case is illustrated in use case no. 1 above. Another such case might involve a music library’s acquisition of a selection of issues from a small music journal. The journal issues acquired by the library do not represent the entire run of the journal, as there are known gaps identified by the issue numbers printed on the cover and spine of the journal. How would BIBFRAME be used to model the entire run of the music journal, including the missing issues?
BIBFRAME has no recommended method of dealing with the issue of missing parts. This problem is especially troublesome for works, events, and instances that are part of a whole and that have a particular sequence. Depending on what type of vocabulary is used to describe the sequencing, the sequence might not be correctly documented or displayed if one or more of the parts are poorly described. For instance, if the parts of a whole are simply described as “next in sequence” within BIBFRAME, the gap created in the sequence will simply be filled as the two parts on either side are placed side by side.
Figure 1. Effect on the sequence of multiple parts if no placeholder is provided for a missing part.
If the metadata of the parts do not make it clear that there is a missing part, the user may never know that the sequencing does not accurately reflect the original resource.
Europeana’s Recommendations for the Representation of Hierarchical Documents in Europeana provides one approach to representing a sequence that has missing parts. The Europeana report suggests creating a placeholder in the form of a “contextual resource” (p. 24). A similar outcome might be achieved in the BIBFRAME model by creating a placeholder.
3.3.6 Other initiatives addressing sequence
Work on aggregate resources in several quarters is relevant to the question of sequence for music resources in BIBFRAME. The FRBR Working Group on Aggregates, in its final report, addressed the concept of an “aggregate manifestation” for resources embodying several expressions of different works. They noted that, in some cases, the aggregate itself constitutes a work with its own relationships (such as to a compiler) and attributes. Their model for these cases added layers for an “aggregating work” realized through an “aggregating expression,” in turn embodied in the aggregate manifestation (p. 4-5). Even though Europeana’s recommendations (introduced above) focused on compound digital objects, the property edm:isNextInSequence could serve as a model for handling the sequence of content units in music resources. Their example of a concert made up of multiple works (p. 34) is relevant to the typical audio disc situation. METS and PREMIS also provide for representation of sequential relationships. Finally, the Variations model of Work – Instantiation – Container has also addressed the questions of aggregates and sequencing for music resources.
3.3.7 Current BIBFRAME support for sequence
BIBFRAME itself does not provide directly for sequences of content units; however, the RDF Collection structure, which can represent an ordered, closed group by means of a list structure (rdf:List, rdf:first, rdf:rest, rdf:nil), may answer this need.
In the current BIBFRAME vocabulary, certain properties have the domain Instance (including contentsNote and duration). The BIBFRAME AV Modeling Study recommends that some of these domain restrictions should be re-examined (p. 42). For example, if some concept of an aggregating resource is in play, bf:contentsNote would need to be used for a Work, not only for an Instance. Similarly, in order to associate description elements with the proper content unit, bf:duration would need to be used for a bf:Work (RDA Expression). The AV Modeling Study also recommends adding date and dateType properties as a way of handling various kinds of dates (p. 43), such as the differing recording dates commonly associated with individual content units of an audio disc. BIBFRAME has not yet developed a thorough approach to medium of performance; these terms are only truly useful in direct association with relevant content.
Assure that the emerging BIBFRAME data environment provides fully for representing sequence relationships among constituent content units and for associating descriptive assertions directly with those units.
Assure that end-user applications serving catalogers and other library data workers address functionality supporting sequence of resources and unambiguous association of descriptive data.
Assure that end-user applications serving library patrons and staff take full advantage of sequence of units and any associated descriptions in search and display.
Because medium of performance statements are currently formulated as lists of instruments, find a way to “wrap” these into a single statement of medium of performance.
Explore possibilities for flexibility of user views of data connected with content units in sequences.
Provide for MARC-to-BIBFRAME conversion without loss of meaning in cases where MARC subfield sequence is significant, such as for medium of performance terms.