recursive xml and xforms?

[inquirydog]

Hello-

XML clearly allows recursive xml (ie- elements to appear in
themselves- examples are in mathml- functions of functions of
functions, or xhtml, tables in tables in tables). My question is
whether xforms can be used to edit such dialects of xml.

To be concrete, consider this toy example- Two elements exist,
<evalope> and <letter>. <envalope> can contain <letter>s and other
<envalope>s as follows.

<envalope name="office mail">
<letter name="tax document" />
<letter name="love letter" />
<envalope name="stuff from fred">
<letter name="xml introduction" />
</envalope>
</envalope>

In theory envalopes could be stored in envalopes that are stored in
envalopes, etc. Now, like with most xml documents I should be able to
create an xforms document that allows me to create and edit this
document. Because of the recursion I don't know if this is possible.
Ideally the user should be presented with an empty "envalope" and
controls that allow them to add and name letters and envalopes. Next
to any envalope that is created a control should exist that allows the
user to add envalopes and letters to it. I know the way to do this
for finite depth, but not in general.

Thanks for the information in advance.

thanks
-I