lang() function and ISO 639

I was looking over the lang() function in XPath under the boolean core
function group (spec. 4.3) and wondered if there was a problem between the
2-letter ISO 639 spec, and the  ISO 639-2:1998 which sets three-letter
codes (http://www.indigo.ie/egt/standards/iso639/iso639-2-en.html).  I
checked Kay's book, and he notes on p. 474 that ". . . if the context node
is the element <para xml:lang="fr-CA"> (indicating Canadian French), then
the expression "lang('fr')" would return true."  Some of the 3-letter
characters--I was once told--in  ISO 639-2:1998 are not similar to allow a
match with just two characters as the spec seems to call for.  I will
double check for incompatible languages, b/c I confess I'm asking this
partly on heresay. 

The xml:lang attribute that is checked by lang() must be declared as such,
just as the case with xml:space, correct?  The QName does not need a
separarte namespace declaration b/c xml: is a default namespace for xml
instances, right?  I'd only need to add that attribute, by my
understanding, yes?

jr

=-=-=-=-=-=-=-=-=-==-=-=-=
John Robert Gardner, Ph.D.
XML Engineer
Emory University
------------------------------------------------------------
http://vedavid.org/diss/
"There is a difference between knowing The Path, and walking the Path."
					-Lawrence Fishburn/Morpheus


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