It is likely that Sandra dropped the milk. It is certain that Brian is a rhino. It is impossible that Mary left the football. It is likely that if either 'Mary left the football' or 'Brian is a rhino' but not both then Bernhard is a swan. We believe that if 'Sandra dropped the milk' or 'Brian is a rhino' or both then John got the milk. It is probably the case that if either 'Brian is a rhino' or 'Sandra dropped the milk' but not both then Lily is a frog.
There is almost no chance that 'Brian is a rhino' or 'Mary left the football' or both.
It is certain that 'Brian is a rhino' or 'Mary left the football' or both.
There is almost no chance that 'Brian is a rhino' or 'Mary left the football' 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.
  1.0::factB.
  0.0::factC.
  %hop1
  0.7::factX:-xor(factC,factB).
  0.75::factY:-or(factA,factB).
  0.7::factZ:-xor(factB,factA).

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

  query(conclusion).
  
'Brian is a rhino' or 'Mary left the football' or both.