WYSIWYG DocBook Editor?

DocBook duck colophon Those of you out there writing DocBook, especially those who do not do a lot of DocBook editing, what open source WYSIWYG DocBook editors do you use?

What DocBook authoring tools to you recommend to folks just getting started with DocBook? For example, what would you recommend for a software developer or architect who has not necessarily worked with a lot of non-WYSIWYG authoring tools? The DocBook authoring tools Wiki page seems to have been lost.

Supported solutions do exist, such as Syntext Serna, XMLmind, and Oxygen XML Editor. What about open source authoring tools, though? Perhaps you have set up XWiki with Wikbook.

Thanks for your suggestions.