The apparatus 17, wherein the program code is configured to identify a set of {HEAD ~ values} that potentially satisfy {TAIL ~ the query} by: 
potentially satisfy
The apparatus 17 , wherein the program code is configured to identify a set of { HEAD ~ values } that potentially satisfy { TAIL ~ the query } by :
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD OTH REL REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH