means for receiving a knowledge sheet serving as an alternate solution when computation of {HEAD ~ said knowledge sheets} of {TAIL ~ the scenario} is a failure, 
of
means for receiving a knowledge sheet serving as an alternate solution when computation of { HEAD ~ said knowledge sheets } of { TAIL ~ the scenario } is a failure ,
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH