It is probably the case that Sandra grabbed the apple. It is highly unlikely that Bernhard is gray. We believe that Brian is white. There is little chance that if 'Bernhard is gray' or 'Sandra grabbed the apple' or both then Mary left the football. It is almost certain that if 'Bernhard is gray' or 'Sandra grabbed the apple' or both then Lily is green. It is certain that if either 'Sandra grabbed the apple' or 'Brian is white' but not both then Julius is a swan.
There is almost no chance that either 'Mary left the football' or 'Lily is green' but not both.
There is a better than even chance that either 'Mary left the football' or 'Lily is green' but not both.
There is almost no chance that either 'Mary left the football' or 'Lily is green' but not 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.
  0.05::factB.
  0.75::factC.
  %hop1
  0.1::factX:-or(factB,factA).
  0.95::factY:-or(factB,factA).
  1.0::factZ:-xor(factA,factC).

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

  query(conclusion).
  
Either 'Mary left the football' or 'Lily is green' but not both.