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