Element <PolicySetIdReference>

Hi, 

I've a problem with the <PolicySetIdReference> Element in XACML.

I've tried several ways of getting the <PolicySetIdReference> work, but I
still get the following error in my java program: 
<Response> 
<Result>
<Decision>Indeterminate</Decision> 
<Status>
 <StatusCode Value="urn:oasis:names:tc:xacml:1.0:status:processing-error"/> 
 <StatusMessage>couldn't resolve policy ref</StatusMessage> 
</Status> 
</Result> 
</Response>

I think with the following XML Expression it has to work: 
<PolicySetIdReference>urn:oasis:names:tc:xacml:1.0:example:policysetid:1</Po
licySetIdReference>

What do you think? 
Is there another way to reference to other Policies or PolicySets? Does the
java program know which file to reference? What's the matter with the
PolicyModule?  

Thanks for your help
NK