If an inexact transformation improves the query performance, {HEAD ~ the system} prioritizes {TAIL ~ the candidate transformation rules} applicable to the selected query element 
prioritizes
If an inexact transformation improves the query performance , { HEAD ~ the system } prioritizes { TAIL ~ the candidate transformation rules } applicable to the selected query element
OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH