From this session S1, the client 20 can perform {HEAD ~ 610 changes} to {TAIL ~ the feature instances} F1 and F2 
to
From this session S1 , the client 20 can perform { HEAD ~ 610 changes } to { TAIL ~ the feature instances } F1 and F2
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH