Tagging meets Subject Headings

Tim has just announced a new LibraryThing feature - the addition of subjects. Now you can look at a book and see both the user-created tags as well as the librarian-assigned subject headings. This puts us in the middle of the age old debate: tags or subject headings? Folksonomies or taxonomies? Ok, maybe the question isn’t quite that old, but it’s certainly debated. Subject analysis is a fuzzy discipline - decisions on "aboutness" are hard. But is it necessarily a question of one over the other? Can they work together at all?

Tags are touted as one of the new great things coming out of Web 2.0. People organize their information using their own vocabulary, deciding for themselves what their books are “about”, and what words they will use to classify them. Tags can also be incoherent, unsystematic, and haphazard. Some tags, like fiction or unread are more useful to the user who provided the tag then to other people. (The unreadable tag which I just discovered, on the other hand, is fascinating!)

There are certainly cases where tags work well. Take Armistead Maupin’s Tales of the City, for example. The top tags include queer and gay fiction, whereas the subject headings are City and town life > Fiction, Humorous stories and San Francisco (Calif.) > Fiction. Someone looking for Tales of the City is unlikely to start their search under City and town life > Fiction (San Francisco, however, might prove a good access point, which is also highlighted in the tags).*

Subject headings, on the other hand, use controlled vocabularies to show hierarchical relationships. They’re assigned by professionals, and are vast, structured, consistent, and organize books into conceptual categories.

Subject headings work great for browsing a subject area, because of their hierarchical structure. Under the tag for civil war is a haphazard collection of books. The subject page for United States > History > Civil War, 1861-1865, on the other hand, provides a list of subdivisions, giving you the ability to do more educated browsing. Interested in the fiction? Historiography? Women in the Civil War?

There are far more subject headings than tags, and their use is indeed a balance of precision. When LCSH terms are too specific, they will pull up only a few books (conversely, if they are too general, thousands appear). Check out the subject heading Married People > Drama which brings up four books in LibraryThing, including two Shakespeare works - but strangely, not Macbeth.

The ordered structure of subject headings gives added meaning. History > Philosophy is very different from Philosophy > History - a distinction that isn't necessarily apparent when searching history or philosophy separately as tags.

Another example - if we look at the tag dystopia, the top two books are 1984 and Brave New World. Interestingly enough, the subject Dystopias gives the exact same top two books. This is also a good demonstration of the binary nature of subjects—something either does or does not belong to a subject. According to the LC, The Time Machine is a dystopia. By contrast, a tag can essentially say The Time Machine is "sort of" a dystopia.

And still, there are times where tags and subjects appear to be enmeshed. Check out Jamie O'Neill's At Swim Two Boys - the tags and subject headings are pretty complimentary.

This comparing and contrasting is getting addictive, but I'll stop. The data's there - go try it yourself!

*[We owe the idea of looking at "gay" and "queer" tags to Clay Shirky's seminal talk/essay "Ontology is Overrated." The phrasing of a low tag score saying something is "sort of" something is David Weinberger adapting Joshua Schachter (source). — Tim]