The identification of {TAIL ~ sub strings} may be performed manually to comprehensively cover a set of {HEAD ~ possible sub strings} or may be performed automatically by tracking queries and discovering which sub strings are frequently searched 
The identification of { TAIL ~ sub strings } may be performed manually to comprehensively cover a set of { HEAD ~ possible sub strings } or may be performed automatically by tracking queries and discovering which sub strings are frequently searched
OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH