These aspects of the invention make it possible to change implementation at {HEAD ~ deployment time}, as opposed to compile {TAIL ~ time} 
These aspects of the invention make it possible to change implementation at { HEAD ~ deployment time } , as opposed to compile { TAIL ~ time }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH REL REL REL REL TAIL TAIL TAIL TAIL TAIL