How to use XML and all its deratives as a tree data structure?

["Trevor Croll" <trevorcroll@fastmail.fm>]

I see lots on all sorts of subjects but the big chunk that is missing for me
is how to use the XML Tree in an application. I have read the DOM specs and
can navigate a  tree, I have written an XMLNoteTree XML editor
http://www.users.bigpond.net.au/tcroll/ .

In this application I can take registration data from/to a form and save as
an XML text file.

I would like to use some standard where the user can specify their form
design and move the form components into place (fixed screen addressing) and
have that form design saved as a usable XML String. When it comes to
designing and writing such an application there is little information about
that would help.

Then when the user wants a report they can write an XSL for that XML and get
XHTML.

When it comes to writing applications for these standards there seems to be
very little to explain how this is done. Are there some good books on XML
Schema, or should I be using Relax NG schemas or something else. It is all
becomming quite confusing.