Each of the levels of scheduling hierarchy might have {HEAD ~ one or more corresponding mapping tables} in {TAIL ~ Queue Engine} 308 
in
Each of the levels of scheduling hierarchy might have { HEAD ~ one or more corresponding mapping tables } in { TAIL ~ Queue Engine } 308
OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL OTH