A block placement generator arranges sets of the interface objects into {HEAD ~ block configurations} within {TAIL ~ the interface} 
within
A block placement generator arranges sets of the interface objects into { HEAD ~ block configurations } within { TAIL ~ the interface }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL