It is probably the case that Bernhard is a lion. It is impossible that Sandra dropped the milk. Chances are about even that John took the apple. It is almost certain that if 'Bernhard is a lion' or 'Sandra dropped the milk' or both then Brian is a frog. It is probable that if 'Bernhard is a lion and Sandra dropped the milk' then Mary moved to the garden. It is highly unlikely that if either 'Sandra dropped the milk' or 'Bernhard is a lion' but not both then Lily is gray.
There is almost no chance that either 'Sandra dropped the milk' or 'John took the apple' but not both.
Chances are about even that either 'Sandra dropped the milk' or 'John took the apple' but not both.
There is almost no chance that either 'Sandra dropped the milk' or 'John took the apple' 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.
  0.0::factB.
  0.5::factC.
  %hop1
  0.95::factX:-or(factA,factB).
  0.7::factY:-and(factA,factB).
  0.05::factZ:-xor(factB,factA).

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

  query(conclusion).
  
Either 'Sandra dropped the milk' or 'John took the apple' but not both.