XMLmind XML Editor v7.3 fully supports DocBook 5.1 --now an OASIS
standard-- out of the box.
DocBook 5.1 assemblies are processed using free, open source, XMLmind
Assembly Processor v1.0. Version 1.0 is the first version to fully
support processing DocBook 5.1 assemblies. This includes XInclude 1.1,
DocBook Transclusion and assembly features such as <relationships> and
<transforms>.