* Written by Jenn Riley *
Article discussed: Alexander, Arden and Tracy Meehleib (2001). “The Thesaurus for Graphic Materials: Its History, Use, and Future.” Cataloging & Classification Quarterly 31(3/4): 189-212.
February’s Metadata Discussion Group session was a lively one. The topic of subject vocabularies beyond LCSH sparked a great deal of interest. The session began with discussion of why a separate subject vocabulary for graphic materials was needed, especially in the Library of Congress. Some participants had even cataloged pictures or posters with LCSH, not knowing that other options existed. Participants realized the need for subject terms that were not in LCSH for describing photographic materials, but recognized the potential to add these terms to LCSH rather than starting a new subject vocabulary. The primary reason for needing a separation of subject vocabularies identified during this discussion was a difference in the level of specificity needed for cataloging visual material as opposed to textual material.
Participants then noted that LCSH and TGM I are structured differently; LCSH is a subject heading list while TGM I is a true thesaurus. While this is an important distinction to understand, the group was uncertain as to the specific implications for practice. Both are standardized vocabularies and are applied in a similar fashion. In the last 15 years LCSH has become more thesaurus-like in standardizing cross-reference structure and describing narrower, broader, and related terms instead of see and see also references.
Overall the discussion group thought that the existence of TGM has struck a reasonable balance between one big general vocabulary and lots of little specific ones. While TGM is specifically focused on graphic images, that is a big space and TGM can be applied in many ways. For a big image collection, a graphic materials-specific vocabulary is a great deal more useful than LCSH would be. The group expected image cataloging (and TGM use) to continue to grow as libraries focus more and more on special collections.
From here, the discussion moved on briefly to comparing the top-down design approach of TGM II with the bottom-up (literary warrant) approach of TGM I. A significant issue with the bottom-up approach was identified – that it is difficult and time-consuming to maintain a robust reference structure for a vocabulary that is constantly growing.
The topic of whether or not to subdivide TGM was a main focus of this month’s discussion. A participant noted that the precoordinated approach has its origins in the printed card catalog, where it was necessary. Now that we are in online systems, this approach can be rethought.The subdivided approach takes more time to apply (this was consensus but nobody knew of data to cite) and it’s not possible to be as specific with geographic locations in subdivisions than it is with postcoordinated geographic headings. Postcoordinated approaches allow the user to decide which feature is of primary interest, rather than having one selected ahead of time. Subdivisions also introduce redundancy as the same subdivisions are often applied to many main headings. But are there cases when they would be different? Would a TGM I heading ever have a different time period subdivision than a TGM II heading on the same record? Perhaps in the case of a contemporary poster of a historic event? It would be more difficult to make this distinction in a postcoordinated approach. A potential benefit of a precoordinated (subdivided) approach is the creation of a browse index. This is achieved in a different way via faceted browsing with the postcoordinated approach. The group felt strongly that the most important goal was to produce a product that is easy and understandable for our usrs. More user studies are needed to learn more about this issue.
The group then wondered what the literature on precoordinated vs. postcoordinated vocabularies looks like. Is there anything recent? Thomas Mann wrote recently on this topic, but no one was aware offhand of other recent work other than Lois Chan describing FAST.
At this point, the discussion turned to the type of training that would be necessary for someone to effectively apply the TGM. For TGM II (genre), the individual would need some level of background with formats of graphic materials. But for topic, participants thought that the same training to perform subject analysis on textual works would apply to graphical works. For some image materials, it is necessary to become familiar with important buildings and people likely to be in the collection, for example buildings on the IU campus and IU presidents for photographs in the University Archives.
The discussion wrapped up with thoughts on the lack of information inherent in the resource that helps with the cataloging process for graphic materials as opposed to textual materials. Generally images come with something that helps identify the content and its origin. Given at least a small amount of information, a cataloger would apply the same type of research techniques, including those applied for authority work, that are already in place in many cataloging units. Image description could be portrayed as an extension of existing work rather than a departure.