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