> I think that my problem was that I couldn't (still can't) 
> understanding why the current context didn't apply to the 
> @href inside the concat expression.
> At what point does the current context ( <a href.. in the 
> default xhtml
> namespace) cease to apply?

The two places in XPath that change the context are (a) the "/" operator -
the context on the right is set by the expression on the left, and (b) the
"[]" operator - the context within the predicate is the item being tested
against the predicate.

Michael Kay
http://www.saxonica.com/