Chances are about even that Sandra left the milk. There is little chance that Fred put down the apple. We believe that Bill went to the garden. It is probably not the case that if either 'Fred put down the apple' or 'Bill went to the garden' but not both then Brian is a lion. There is a better than even chance that if 'Sandra left the milk' or 'Fred put down the apple' or both then Mary took the football. It is probably the case that if either 'Sandra left the milk' or 'Bill went to the garden' but not both then Bernhard is a swan.
It is almost certain that 'Sandra left the milk' or 'Mary took the football' or both.
Chances are about even that 'Sandra left the milk' or 'Mary took the football' or both.
It is almost certain that 'Sandra left the milk' or 'Mary took 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
  0.5::factA.
  0.1::factB.
  0.75::factC.
  %hop1
  0.25::factX:-xor(factB,factC).
  0.6::factY:-or(factA,factB).
  0.7::factZ:-xor(factA,factC).

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

  query(conclusion).
  
'Sandra left the milk' or 'Mary took the football' or both.