There is a better than even chance that Sandra dropped the milk. It is probably the case that Gertrude is a sheep. It is impossible that Bernhard is green. It is impossible that if 'Sandra dropped the milk' or 'Gertrude is a sheep' or both then Greg is yellow. It is impossible that if 'Gertrude is a sheep' or 'Bernhard is green' or both then Mary took the football. It is probably the case that if 'Sandra dropped the milk' or 'Bernhard is green' or both then Julius is a lion.
It is impossible that either 'Julius is a lion' or 'Mary took the football' but not both.
Chances are about even that either 'Julius is a lion' or 'Mary took the football' but not both.
It is impossible that either 'Julius is a lion' or 'Mary took the football' 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
  0.6::factA.
  0.7::factB.
  0.0::factC.
  %hop1
  0.0::factX:-or(factA,factB).
  0.0::factY:-or(factB,factC).
  0.7::factZ:-or(factA,factC).

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

  query(conclusion).
  
Either 'Julius is a lion' or 'Mary took the football' but not both.