The RA provides {HEAD ~ a subsystem} with {TAIL ~ a mechanism} for sending read and write request to the DA of another subsystem 
The RA provides { HEAD ~ a subsystem } with { TAIL ~ a mechanism } for sending read and write request to the DA of another subsystem
OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH