XML Schemas

Hi,

My teammate and I are currently working on a web based XML editor (that
extracts XML files from rars/jars/wars and ears) to configure
applications running on an application server while they're still
deployed.

One of the editor's views is a form based view. You can take a look at a
simple mock-up of the UI we are building at:
http://people.redhat.com/pasmith/third.html

We are required to validate the XML against its associated schemas.
Though we also need to get information from the schema for the UI.  For
example, if the schema specifies that only 3 specific elements can be
added as children to an element, then the form will have a drop down
menu with only those 3 options.  

My question is, are there any existing projects or APIs available that
will help in loading a schema and extracting such information.

At the moment we are already using Xerces for our XML processing and
validation.

Thanks a lot.

Patrick Smith