Expanded name/URI for xml: namespace?

["John E. Simpson" <simpson@xxxxxxxxxxx>]

Section [5/4] in the XPath spec begins:

   Each element has an associated set of namespace nodes, one for
   each distinct namespace prefix that is in scope for the element
   (including the xml prefix, which is implicitly declared by the
   XML Namespaces Recommendation) and one for the default namespace
   if one is in scope for the element.

My question pertains to that parenthetical aside: Does this imply that the 
xml prefix is by default in scope for any XML document? (Not counting 
documents which have an xmlns="" attribute; per the note in this section, 
"An attribute xmlns='' 'undeclares' the default namespace.")

If this is the case, what is the expanded name of this namespace node? I've 
searched several resources, including the namespaces Rec, XML-DEV archives 
(to the extent possible), this list's archives, Mike Kay's book, and so on, 
and have (interestingly!) found no sign of a URI which is mapped to the 
xml: prefix. (Some older messages on XML-DEV, prior to the final Namespaces 
Rec, mention xmlns:xml="http://w3.org"; but that seems spurious or at least 
just intended for illustrative purposes.) Is there one? Should there be, in 
a compliant (=XPath-aware) processor?

Any guesses (or preferably, certainties :)?

======================================================================
John E. Simpson         | "I used to be an airline pilot. I got fired.
http://www.flixml.org   | I kept locking the keys in the plane. They
simpson@xxxxxxxxxxx     | caught me on an 80-foot stepladder with a
                        | coathanger." (Steven Wright)


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