For those who do not follow the nxml list as well. I found a solution
at
http://tech.groups.yahoo.com/group/dita-users/message/6711
Basically, it's first Florent Georges' approach, then manually changing
the start declaration of each generated RNC schema (well, actually I
only needed to change some of them. Some were ok).
A working schema can be found as an attachment to this message:
http://permalink.gmane.org/gmane.emacs.nxml.general/1634
