There is a better than even chance that Julius is a swan. It is highly likely that Brian is a rhino. There is a better than even chance that John went to the kitchen. There is almost no chance that if either 'Julius is a swan' or 'John went to the kitchen' but not both then Mary dropped the milk. Chances are about even that if either 'John went to the kitchen' or 'Julius is a swan' but not both then Gertrude is a sheep. It is probable that if either 'Brian is a rhino' or 'Julius is a swan' but not both then Sandra grabbed the apple.
We believe that 'Gertrude is a sheep' or 'Mary dropped the milk' or both.
It is probably not the case that 'Gertrude is a sheep' or 'Mary dropped the milk' or both.
We believe that 'Gertrude is a sheep' or 'Mary dropped the milk' 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
  0.6::factA.
  0.9::factB.
  0.6::factC.
  %hop1
  0.02::factX:-xor(factA,factC).
  0.5::factY:-xor(factC,factA).
  0.7::factZ:-xor(factB,factA).

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

  query(conclusion).
  
'Gertrude is a sheep' or 'Mary dropped the milk' or both.