It is impossible that Julius is a rhino. It is probably not the case that Winona is a mouse. It is probable that Mary left the football. Chances are about even that if 'Mary left the football' or 'Winona is a mouse' or both then Bernhard is white. It is almost certain that if either 'Mary left the football' or 'Winona is a mouse' but not both then Greg is a frog. Chances are about even that if either 'Julius is a rhino' or 'Winona is a mouse' but not both then Sandra grabbed the milk.
It is improbable that either 'Greg is a frog' or 'Sandra grabbed the milk' but not both.
There is a better than even chance that either 'Greg is a frog' or 'Sandra grabbed the milk' but not both.
It is improbable that either 'Greg is a frog' or 'Sandra grabbed the milk' 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
  0.0::factA.
  0.25::factB.
  0.7::factC.
  %hop1
  0.5::factX:-or(factC,factB).
  0.95::factY:-xor(factC,factB).
  0.5::factZ:-xor(factA,factB).

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

  query(conclusion).
  
Either 'Greg is a frog' or 'Sandra grabbed the milk' but not both.