Element equivalence under XML Namespaces

Would any XML/Namespaces guru be willing to answer the following
question for me?  Is the following a well-formed XML document:

<?xml version="1.0"?>
<doc xmlns="http://foo.com/foo">
   <foo:elem xmlns:foo="http://foo.com/foo">
   </elem>
</doc>

My question is a question of equivalence under XML namespaces.  Because
the namespace names and local names are the same for <foo:elem>
and </elem> is it permitted under any flavor of the XML and XML
Namespaces standards to close <foo:elem> with </elem> or is that an
error?

Forgive me if this has been answered somewhere already, I've
searched the standards, the archives for xml-dev, comp.text.xml, and
various spots on the web and I haven't been able to determine if the
above construction is permitted, forbidden, or left up to the parser
implementation to determine.

Thanks so much,
Matt Van Gundy