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