Custom XML format for compatibility with DocBook

Hello,

The Italian Pluto Journal, an e-magazine dedicated to Linux, is
currently developing an automated solution to submit/revise/approve
articles using XML. The article file should be compatible with DocBook,
maybe a subset of it, so that we can use OpenOffice to edit/convert the
files in other formats.

I know that there exist SimpleDocBook, but that sounds as a vast format
nontheless, so I was wondering if anyone else has done something like
this and what approach did he/she use.

TIA for any pointer,

Andrew