NameId question

[Peter Schober]

* Brewer, Edward L <lee.brewer at Vanderbilt.Edu> [2013-02-26 21:00]:
> resolver:Dependency ref="concurid" /><resolver:AttributeEncoder
> xsi:type="SAML2StringNameID"
> xmlns="urn:mace:shibboleth:2.0:attribute:encoder"
> nameFormat="urn:oasis:names:tc:SAML:2.0:nameid-format:transient" />

But why the transient nameFormat? uid at vu is not reall transient,
-peter