There is almost no chance that Daniel dropped the apple. It is highly unlikely that Bernhard is a lion. It is improbable that Sandra took the milk. It is probably the case that if 'Daniel dropped the apple' or 'Sandra took the milk' or both then Greg is a frog. It is impossible that if 'Bernhard is a lion and Sandra took the milk' then Gertrude is a mouse. There is a better than even chance that if 'Daniel dropped the apple and Bernhard is a lion' then Lily is gray.
There is little chance that either 'Greg is a frog' or 'Lily is gray' but not both.
There is little chance that either 'Greg is a frog' or 'Lily is gray' but not both.
It is probable that either 'Greg is a frog' or 'Lily is gray' 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
  0.02::factA.
  0.05::factB.
  0.1::factC.
  %hop1
  0.7::factX:-or(factA,factC).
  0.0::factY:-and(factB,factC).
  0.6::factZ:-and(factA,factB).

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

  query(conclusion).
  
Either 'Greg is a frog' or 'Lily is gray' but not both.