It is likely that Brian is a swan. It is probably the case that Bernhard is a frog. It is highly likely that Greg is yellow. There is almost no chance that if 'Brian is a swan' or 'Bernhard is a frog' or both then Mary went to the hallway. It is highly unlikely that if 'Greg is yellow and Brian is a swan' then Sandra grabbed the milk. It is highly unlikely that if 'Greg is yellow and Brian is a swan' then Lily is a lion.
It is certain that 'Lily is a lion' or 'Mary went to the hallway' or both.
It is highly unlikely that 'Lily is a lion' or 'Mary went to the hallway' or both.
It is certain that 'Lily is a lion' or 'Mary went to the hallway' 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
  0.7::factA.
  0.7::factB.
  0.9::factC.
  %hop1
  0.02::factX:-or(factA,factB).
  0.05::factY:-and(factC,factA).
  0.05::factZ:-and(factC,factA).

  %hop2
  conclusion:-or(factZ,factX).

  query(conclusion).
  
'Lily is a lion' or 'Mary went to the hallway' or both.