Folksonomy is an emerging practice on the Internet where people tag digital artifacts (e.g., pictures, bookmarks) with their own labels and then share them. Of course, people in the real world have been tagging and sharing collections for years; consider record and coin collections with tags like classical, rock, jazz, Merovingian, etc. One factor that makes tagging on the Internet different is that items and their tags can be shared with the world at large very easily, allowing for an emergent understanding of how common, tagged items are viewed by a large number of people. Further, folksonomy tagging with web-based tools (e.g., flickr and del.icio.us) is also very easy.
As a result of ease of tagging and sharing, folksonomy is spreading on the web like wild fire. Fickr, the folksonomy-based photo sharing service, has over 300,000 users, and Robert Scoble has signaled folksonomy tagging to Microsoft's senior management as an area requiring strategic investment.
Currently, all folksonomy data formats are proprietary and idiosyncratic to the service providing them, likely as a result of folksonomy's ad hoc development to date. There is no easy way to transfer one's data from one service to another. Further, there is currently no format for sharing or even expressing one's explicit understanding of the meaning of his/her own folksonomy tags. Tag and object tagged mutually and implicitly define each other without an explicit anchor point.
In this post I will motivate and sketch xFolk, a microformat for specifying and publishing folksonomies using components already part of xhtml. Since xhtml is already a well-established web standard, a compelling motivation for creating the xFolk microformat is that it will enable users to independently maintain their own folksonomy data while still being able to easily share it. A byproduct is that xFolk will allow those who wish to define explicit semantics for their folksonomy tags to do so, and these semantics will also be easily shared.
xFolk is inspired by Eric Meyer's and Tantek Çelik's panels at SXSW 2005 on emergent semantics and extending xhtml. My thoughts are at a very early stage and might even be termed a pre-proposal, but I am publishing them here because I think they are sufficiently developed to profit from community interaction.