Norm Walsh has released the latest beta of the DocBook v5.0 schemas. More information is available at: http://norman.walsh.name/2006/07/28/docbook50b7.
This version includes the recently approved "audience" effectivity attribute, so you have a little more flexibility in profiling your documents. Before, you had to squeeze this kind of profiling into userlevel, vendor,condition or role. This attribute provides another level of distinction, so you can create an output comprised of both userlevel AND audience, etc.