Bill Ives points to a Good Article on Tagging – HP Labs:
Pito Salas of BlogBridge sent me a link to a great article on the concepts behind and within tagging, The Structure of Collaborative Tagging Systems by Scott Golder and Bernardo A. Huberman, Information Dynamics Laboratory, HP Labs. They describe collaborative tagging as "the process by which many users add metadata in the form of keywords to shared content".This is what is commonly referred to as tagging at the moment and what was popularized by sites such as del.icio.us and Flickr. In the abstract write that they "discovered regularities in user activity, tag frequencies, kinds of tags used, bursts of popularity in bookmarking and a remarkable stability in the relative proportions of tags within a given url. We also present a dynamical model of collaborative tagging that predicts these stable patterns and relates them to imitation and shared knowledge".
Earlier, I did a brief general introduction to tagging.