AttributeSelector - Missing Attribute

Hi All,

If I used an XPath expression in an AttributeSelector, that was not available in the request context - resource content, would the PDP return "Indeterminate" or "Not Applicable"?? 

Is it possible to use the following : 

<ResourceMatch MatchId="urn:oasis:names:tc:xacml:1.0:function:integer-less-than">

   <AttributeValue DataType="http://www.w3.org/2001/XMLSchema#integer">0</AttributeValue>

<AttributeSelector RequestContextPath="count(//gml:position)" DataType="http://www.w3.org/2001/XMLSchema#integer"/>

</ResourceMatch>

in the policy target to check if there are elements of a certain type in the request before looking for them in that policies rules?

Thanks in advance,
Michael