Converting DocBook4 to DocBook5
Within the Zend Framework 2 repository, I recently performed a conversion from DocBook 4 to 5. The latter is a more modern version of the toolchain, and offers a somewhat simpler syntax and workflow. For example, you no longer need to track how many levels deep you are in your chapter sections -- you simply use a tag. One of the nicer changes is that you do not need to specify a doctype any more; you simply declare XML namespaces on your root elements and continue merrily on your way. This actually allows us to remove some actions in our build process, and makes validation much simpler.
Interestingly, for DocBook5 being available in beta since 2005 and an official standard since 2009, there is very little material on migrating from DocBook 4 to 5.