We believe that Bernhard is yellow. It is improbable that Jeff dropped the apple. There is little chance that Brian is a lion. It is almost certain that if 'Jeff dropped the apple' or 'Brian is a lion' or both then Greg is a swan. It is certain that if 'Bernhard is yellow and Jeff dropped the apple' then Lily is a rhino. There is little chance that if 'Bernhard is yellow and Jeff dropped the apple' then Mary went to the garden.
We doubt that 'Lily is a rhino' or 'Greg is a swan' or both.
We doubt that 'Lily is a rhino' or 'Greg is a swan' or both.
It is certain that 'Lily is a rhino' or 'Greg is a swan' 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
  0.75::factA.
  0.1::factB.
  0.1::factC.
  %hop1
  0.95::factX:-or(factB,factC).
  1.0::factY:-and(factA,factB).
  0.1::factZ:-and(factA,factB).

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

  query(conclusion).
  
'Lily is a rhino' or 'Greg is a swan' or both.