It is highly likely that Brian is a frog. There is almost no chance that John got the apple. It is highly likely that Greg is a lion. We believe that if either 'John got the apple' or 'Greg is a lion' but not both then Sandra put down the milk. It is probably not the case that if 'John got the apple' or 'Greg is a lion' or both then Gertrude is a cat. We believe that if 'John got the apple and Greg is a lion' then Julius is a rhino.
It is probably not the case that 'Gertrude is a cat' or 'Julius is a rhino' or both.
It is probably not the case that 'Gertrude is a cat' or 'Julius is a rhino' or both.
It is probable that 'Gertrude is a cat' or 'Julius is a rhino' 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
  0.9::factA.
  0.02::factB.
  0.9::factC.
  %hop1
  0.75::factX:-xor(factB,factC).
  0.25::factY:-or(factB,factC).
  0.75::factZ:-and(factB,factC).

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

  query(conclusion).
  
'Gertrude is a cat' or 'Julius is a rhino' or both.