XML Support related questions

Hello PostgreSQL XML Experts,

I was exploring xml support in postgreSQL and ran into few questions
answer to which I couldn't find easily in the documentation. I would
appreciate responses to following queries:

1) Can xml column be constrained to be DOCUMENT or CONTENT type?

XMLPARSE/XMLSERIALIZE functions allows to set XML option DOCUMENT or
CONTENT type. Can we do the same when defining an xml column level?

2) Is there plan in near future to support XML schema validation
i.e to ensure inserted xml document conforms to a preregistered set of
XML schemas.

3) Support for XQuery - I know it is asking for too much but when
do you see it happening in the future.

4) Support for xml indexes - Is it something that is being worked
upon for next release?

Our application support many underlying databases and I would hate to
list out the stuff users cannot do when using xml datatype in
postgresql. So far for non-xml functionality we haven't had to this and
I hope I don't need to do it for xml as well.

Thanks,

Brijesh