It is certain that Greg is gray. There is almost no chance that Gertrude is a cat. There is little chance that Lily is a lion. It is highly likely that if either 'Gertrude is a cat' or 'Lily is a lion' but not both then Sandra got the milk. We believe that if 'Greg is gray and Gertrude is a cat' then Mary left the football. It is highly unlikely that if 'Lily is a lion and Greg is gray' then Daniel dropped the apple.
There is little chance that 'Lily is a lion' or 'Greg is gray' or both.
It is certain that 'Lily is a lion' or 'Greg is gray' or both.
There is little chance that 'Lily is a lion' or 'Greg is gray' or both.

  and(A,B) :- A,B.
  or(A,B) :- A;B.
  nand(A,B) :- not(and(A,B)).
  nor(A,B) :- not(or(A,B)).
  xor(A,B) :- or(A,B), nand(A,B).

  %hop0
  1.0::factA.
  0.02::factB.
  0.1::factC.
  %hop1
  0.9::factX:-xor(factB,factC).
  0.75::factY:-and(factA,factB).
  0.05::factZ:-and(factC,factA).

  %hop2
  conclusion:-or(factC,factA).

  query(conclusion).
  
'Lily is a lion' or 'Greg is gray' or both.