DocBook V5.0 is in the namespace
A version attribute is now required on the root element.
Element and attribute names are case-sensitive (as they have been in the XML DTD since 4.0).
Content models are generally simpler.
Uses XLink; allows most inlines to be link elements.
Many constraints are now enforced by the grammar. They are not new, but they could not previously be enforced by DTDs.
A few simple datatypes are used.
Accessibility has been improved with the introduction of