In the halls and session rooms at the OReilly Emerging Technology Conference here, a series of talks this week explored the growing use of tags to let users associate keyword metadata to Web information.
Among the early implementers of tags are Ludicorps Flickr photo-sharing site, the del.icio.us social bookmarking service and the Wikipedia collaborative online encyclopedia. During one conference session, leaders from the three upstart services explored the impact of their decisions to turn categorization over to individuals rather than enforcing established categories.
Tags are creating more than straightforward classifications of Web documents or links, said Joshua Schachter, the creator of del.icio.us. One of the most popular tags created on the bookmarking service is "to_read," a tag attached to links of pages users want to remember to read.
"There is a behavior around tags that has nothing to do with categorization," Schachter said.
On del.icio.us, users create one-word tags for Web pages as they bookmark them in the service. Users can sort and view their bookmarks by various tags, while also viewing the Web links associated with the most popular tags among all users.
Even the new term "Folksonomy" has emerged to describe the potential for user-defined tags to organically develop structure out of what might appear to be chaotic collections of information.
One of the uncertainties about tags is how they can fit together among various services and what meaning can be gleaned from the tags of a large mass of users.
Efforts to collect tags broadly have begun. Earlier this year, Weblog search engine Technorati Inc. started supporting tags. The site now tracks tags from photos in Flickr, bookmarks stored in del.icio.us and LookSmart Ltd.s Furl service, and blogs published with tags.
Tags arent without their drawbacks. Stewart Butterfield, Ludicorps president and founder, noted how in Flickr an individuals tag of a photo might be a mismatch for another user.
For example, a user who travels to Tokyo might tag all photos from the trip as "Tokyo," including those taken inside a hotel room, Butterfield said. But other users might expect to see only photos of the Tokyo cityscape, and not a hotels interior, when viewing photos tagged as Tokyo.
"I dont think in the context of Flickr that there are bad tags," Butterfield said. "The point is not for you to find all of and only pictures of elephants but to give people a few extra tools to organize their own stuff."
Similarly, del.icio.us focuses more on individuals, avoiding approaches where the service might suggest or steer users to use any specific tags, Schachter said.
"I dont want people to be dominated by group think," Schachter said. "Its your instinct that is the most reliable and reproducible thing."
Yet for Wikipedia, tags complement its group approach for organizing the popular online encyclopedia. Jimmy Wales, co-founder of Wikipedia, said the project relies on a core group of between 600 and 1,000 people to manage the encyclopedia and that the group collectively corrects misclassifications.
"If you start tagging things in the wrong way in the encyclopedia, youll hear about it right away," Wales said.
Wikipedia last summer launched its categorization system for the encyclopedia, and Wales said that opening classification to individual project contributors fit with Wikipedias collaborative approach.
"As to why we decided to let the masses categorize things, it never occurred to us to ask that question," he said.