XML Challenge

Hi everyone! I'm new to this list.  Does anyone know where I can find
information regarding XML functionality in postgreSQL? Also, I could
probably use some general advice...

I'm working on a large project, and I'm running into an interesting
challenge:

My client is a testing lab, and they frequently develop new tests to
perform for their clients. Right now they handle everything with paper
worksheets. I am tyring to help them eliminate the paper-pushing.

I would like to enable the users to create electronic, preferably
web-based data-entry forms on their own. I want to create this solution
in such a way that in the process of designing the fields and forms they
would automatically and dynamically create and edit tables in a
database, possibly seperate from the main postgreSQL database.

I am using 7.4.1 and PHP 4 so far.  I've briefly looked at the Microsoft
InfoPath product, which looks like it will create an xml schema from the
forms created in the program, which I guess might be 1/2-way there since
I could probably use the schema to define tables/etc...

Ideally, I am hoping to find an open-source solution that uses the new
W3C XForms specification.  However, I can't find any form
designers/editors equivalent to InfoPath for linux/open-source and MS
Infopath doesn't support XForms. I've also come upon Mozilla XUL a lot
in my research and am curious if any of you have experience with that,
as well.

Any input is greatly appreciated.

Kind Regards,

    -Ryan Riehle
     President, BuildWays Corporation