The original intent was to create an interesting, fun project which was both useful and would demonstrate the Python XML processing software which was being developed at the time. Mark Hammond contributed the original idea, and other members of the SIG chimed in to add support for their favorite browser features. After debate which ranged far afield from the original idea, compromises were reached which allow XBEL to be a useful language for describing bookmark data for a range of browsers, including the major browsers and a number of less widely used browsers.
At this time, the formal document type definition (DTD) was finalized and documentation was written. These are available online here.