Attribute values or the lack therof

Hi fellow SAML'ers,

How should an implementation send an empty value (i.e. like a NO-VALUE value
in a database) for an attribute?  The first idea I had was to send an
Attribute element with no AttributeValue but that seems to be explicitly
forbidden by the schema (no minOccurs attribute which means 1 is required, I
think).  The second idea I had was to just specify an empty element (like
<AttributeValue/> or <AttributeValue></AttributeValue>) but section 1.2.1 of
the core spec (Assertions and Protocol, etc.) seems to disallow this.

A similar problem comes up with trying to send an empty string (i.e. "").

Have any other implementers solved this?

David
--
Obligatory .signatory
David Warren       phone: 781-515-7152
RSA Security Inc., 174 Middlesex Turnpike, Bedford, MA 01730