ISSUE-73: Do we allow DTDs, external entities, etc.

ISSUE-73: Do we allow DTDs, external entities, etc.

http://www.w3.org/2005/06/tracker/databinding/issues/73

Raised by: Paul Downey
On product: Basic

Currently we define document conformance in terms of the XML 1,0 using patterns
defined using the XPath 2.0 datamodel. We don't use Infoset terminology.
This could be problematic, in particular, do we appear to disallow the use of
XML entities in XML Schema documents, something which may be useful, if not
widely supported?

Should we explicitly allow or disallow DTDs in Basic Schema documents?