Updated text to read:

WS-SecurityPolicy token assertions specify the type of tokens required during communication.  Unfortunately, the WS-SecurityPolicy specification does 
not provide a way to bind an actual token within a token assertion.  This functionality is desirable as a means of using endpoint references for key 
distribution.  For example, consider an EPR containing policy describing a security mechanism (e.g., message-level encryption) that requires the 
INITIATOR to use a token (e.g., an X.509 certificate) identifying the RECIPIENT. In this case, it is convenient to furnish the actual RECIPIENT token 
along with the security policy within the EPR.