When thinking about bibliographic data (for example) and social applications using taggings, it’s pretty easy to think that the data (title, author, and so on) is highly structured and therefore very different from tags, which are freeform and all that jazz. In many ways, that’s true, and it’s especially important for the purposes of bibliographic control. But in social applications where users are contributing data, the line can get a lot fuzzier. LibraryThing is an example: users contribute various structured and unstructured data about books. Some of the data comes from libraries or Amazon, some is put in by hand, and some of the library- or publisher-supplied data is cleaned up by users, because it’s not always right. Users can enter structured information in fields—information about the item in general like title and author, but also personal information, like ratings and the date it was read. They can also enter tags and search and sort books by those tags.
Flickr has just introduced “machine tags” (or “triple tags”). These build on existing geotags, which encode locations like this:
geo:long=123.456. They’re three-part tags, with a namespace and a key-value pair, and you could use them to express all manner of things—like, for example
dc:title=Othello. (There are also some semi-official uses of namespaces on tags in del.icio.us, like system:unfiled and filetype:mp3, and various users have used namespaces and triple tags on services like these without official support.) You might think of them as a kind of really lightweight RDF.
Triple tags really blow away the distinction between structured fields and freeform tags. This is important, because it’s a step along a road in which it’s easier for Joe and Jane User to make sense of complicated sets of data by sorting and filtering. Once you’ve become comfortable searching and sorting your tags, it’s not too much of a stretch to apply the same tools to more structured data. Sure, maybe it’s the same data that’s always been there, but now maybe Jane User could be better at manipulating it because she doesn’t have to understand “databases”, she just has grok “tags”, along with a little lightweight syntax. It’s just a different way of looking at the data, one that might prove more friendly. I know not all the tools are there yet, and I’m certainly not saying that everybody’s grandma is going to be putting machine tags on Flickr tomorrow, but I think this is a step in the right direction.