The computer implemented method 1 further comprising determining {TAIL ~ said improved index performance indicator} by using {HEAD ~ a query box} 
The computer implemented method 1 further comprising determining { TAIL ~ said improved index performance indicator } by using { HEAD ~ a query box }
OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD