Namespace moves

[Nick Sydenham]

I'm looking at an existing problem with some of our code and couldn't 
find a definitive answer in the W3C Recommendation. Basically, it's not 
clear from the spec how moving a namespace definition affects the 
validity of a signature. For instance, if I have:

<SignedInfo xmls:gt="http://www.wibble.com/CM/envelope";>
...
<Transform Algorithm="...">
        <XPath>(count(ancestor-or-self::node()/gt:Message/gt:Body)=...
</Transform>
</SignedInfo>
If I then return an enveloping signature with the gt namespace moved to 
the root element the XML document is still valid as the namespace is 
still declared on an ancestor node. However, from an XML Signature point 
of view I have changed the SignedInfo element which in theory breaks the 
signature. Is this a correct analysis or should moving the namespace 
definition not affect the signature validity?

TIA,
Nick