RE: Documents with both XSD and DTD

> > Can a document safely reference both a DTD (via <!DOCTYPE ... >)
> > and an XML Schema Document?

Yes.

> > 
> > And does a DTD require/allow an XML prolog? 

I believe that an entity used to hold the external DTD subset can have a
text declaration <?xml ...?> just like any other external entity, though
they seem to be rarely used in practice. Try it and see. I assume this is
what you meant by the question. A DTD can't include an XML prolog because
the prolog allows a DOCTYPE declaration, and DTDs can't be nested except by
using parameter entities.

This is completely off-topic for this list.

Michael Kay
http://www.saxonica.com/