Docbook-xml mode is an early implementation of a Major Mode for Docbook XML written by FrancisLitterio.

Docbookxml project page - Located at Sourceforge and characteristically inactive.

docbook-xml-mode.el - Latest version in web CVS.


DocbookIDE – Major mode for editing Docbook SGML/XML. Has been VaporWare since 2000.

It’s worth taking a look into PsgmlMode.

And why not NxmlMode which comes with Docbook support?