The system applies {TAIL ~ the transformed inexact query output} to {HEAD ~ a heterogeneous datastore} to provide an output query result 
The system applies { TAIL ~ the transformed inexact query output } to { HEAD ~ a heterogeneous datastore } to provide an output query result
OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH