If the transformed remote query element is pushdownable to one of the heterogeneous datastores, {TAIL ~ the present system} adds the transformed remote query element to {HEAD ~ a transformed inexact query output} 
If the transformed remote query element is pushdownable to one of the heterogeneous datastores , { TAIL ~ the present system } adds the transformed remote query element to { HEAD ~ a transformed inexact query output }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD