You mentioned that Serna internally converts DTD-specified XML dialects to
the equivalent XML Schema specification. That hasn't been my experience.
If you want to be able to validate in Serna, you have to generate an XML
Schema from your DTD using a separate tool that you can download from their
site. It does a good, if not perfect, job of converting. I had to tweak a
couple of lines in the generated XML Schema to get DocBook 4.5 to work.
For DocBook 5, there is an XML Schema already generated, as part of the
complete set of schemas for DB5.
Bob Stayton
Sagehill Enterprises
DocBook Consulting
bobs@sagehill.net