The SA is responsible for responding to requests from {TAIL ~ the DA} of {HEAD ~ another subsystem} 
The SA is responsible for responding to requests from { TAIL ~ the DA } of { HEAD ~ another subsystem }
OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH HEAD HEAD HEAD HEAD HEAD HEAD