do computed namespace add to in-scope namespaces?

Section 3.7.3.7 "Computed Namespace Constructors" states
a computed namespace constructor "adds the namespace
prefix to the in-scope namespaces for its encloding
arguments".  But how is this possible?  The in-scope
namespaces are part of the *static context*, and the
name and content expressions are both evaluated at
run-time.

Is this valid?  I would assume not.

element foo {
   namespace {"ns"} {"..."},
   <ns:bar />
}
-- 
	--Per Bothner
per@bothner.com   http://per.bothner.com/