There are cases where the creation of an enumeration is done by an entity 
that is separate from the resulting dataset itself.  In these cases the 
same endpoint may not be responsible for both creating the enumeration 
context and for iterating over it.  To support these cases the 
EnumerateResponse element should be extended to have an optional EPR 
returned that must then be used for the Pull/Release() requests instead of 
the original EPR.

Proposal:
Extend the EnumerateResponse with the wsen:EnumerateEPR
    <wsen:EnumerateResponse ?>
      <wsen:Expires>[xs:dateTime | xs:duration]</wsen:Expires> ?
      <wsen:EnumerationContext>?</wsen:EnumerationContext>
      <wsen:EnumerateEPR> wsa:EndpointReferenceType </wsen:EnumerateEPR> ?
      ?
    </wsen:EnumerateResponse>

/EnumerateEPR
When present this element is the EPR to which all subsequent Pulls and 
Release operations must be sent. It is up to the data source to decide 
whether or not to include this element