xml form editor <-> kupu

dear developers

(silva-1.1.1-all, completely new silva root)

i noticed an inconsistency in the generated xml by form editor and kupu:

form editor
-----------
<?xml version="1.0" ?>
<doc>
   <p type="normal">this is a test.
   </p>
</doc>

kupu
----
<?xml version="1.0" ?>
<doc xmlns="http://xml.infrae.com/document/0.9.3">
   <p type="normal">this is a test.
   </p>
</doc>

as soon as you work with/ change to kupu a doc attribute gets added; it 
looks like some kind of version note. but version of what? the silva 
product? the silva xml schema?
as long as you work with the form editor the doc attribute never gets 
added.
which of the generated xml is the correct one?

regards,
marc