I was on the road last week and didn't have a chance to post the GREAT news!
At the DocBook TC meeting on November 7, 2007, DocBook V5.0 was approved as a Committee Draft! This draft was a result of several years of hard design work, especially by Norm Walsh, who created 9 Beta Releases and 7 Candidate Releases since October of 2005.
The most exciting feature, IMO, that this standard is based on RelaxNG rather than DTD. DTD and XSD are still supported/provided, but the canonical format is now RelaxNG (RNC). Vendors, start your engines and add support for RelaxNG validation! Actually, several vendors are already "ahead of the game" with RelaxNG support: oXygen XML Editor, XML Mind XXE, Editix, Emacs nXML, Cladonia Exchanger XML Editor. Conspicuously missing: PTC Arbortext Editor and XMetal. [NUDGE: C'mon big guys!]
The other exciting result of DocBook v5 and RelaxNG, is that it makes customization layers EXTREMELY easy to manage. The DocBook Subcommittee for Publishers proposed a new modularization of the RNC schemas for DocBook v5 to create Core DocBook and additional schema modules, which have now been incorporated into the v5 source. As a result, we've also been able to produce an initial draft of an official DocBook Publishers customization very easily!
This is great news for the entire DocBook TC and community!