Another strategy for tagging is illustrated by CBBC, the BBC's site with children's content.  Workers tag the site content internally, so that a search for animals, for example, will lead to articles and videos about pets and wildlife yet keep the searcher within the children's area of the site. In contrast to CBBC or Google Video, which limit users to particular sites, Blinkx allows the user to search over 7 million videos (and podcasts) stored at dozens of archives around the Internet. The sheer magnitude of the search brings home the significance of tagging, that is, how producers themselves define their content. For example, with the search terms culture and Thailand I found 74 videos. One of these had some 35 tags, including Less than 10 Seconds, Non US Location, Real Time, and Cinematography. Also among the search results was a podcast from Stanford University with no apparent relationship to the two search terms; yet with a little digging, I found the term culture in the sidebar list of topics at the Web site where the podcast was housed. This kind of breadth and depth of search can be daunting, and emphasizes the necessity of good producer tagging.

Tags are especially important for non-text files, e.g., video, photos, graphics, audio, and music. Some sites use visual referencing to indicate the number of related tags. For example, at the jamendo search engine, the relative size of the tag indicates the relative number of matches within their database as seen in Figure 4.

Figure 4. jamendo demonstrates the number of matches to their database by the size of the producer-defined tag. http://www.jamendo.com/.

One of the chief ways to use tagging is to find others with like interests. Once found, a photo blog, vlog, or podcast can then be followed via RSS (really simple syndication), with one of the many applications such as Bloglines and Furl that find and retrieve new information from user-designated sites. (Bloglines is an aggregator that sends the new information to a Website visited by the user; Furl sends new information to the user's email address.) One recently organized EFL composition project, WritingMatrix, is using precisely this combination of tagging and RSS to stimulate student blogging. In future, face recognition software and speech-to-text capabilities will enable search engines to find video and audio content, but these are still far from perfect. Until this more sophisticated type of software becomes readily available, tags enable organization of the myriad sites on the Web and increasingly are enabling collaborations to take place.