It is certain that Sandra got the football. It is improbable that Jeff put down the milk. It is highly unlikely that Bernhard is a rhino. Chances are slight that if 'Sandra got the football' or 'Jeff put down the milk' or both then Greg is a lion. Chances are about even that if either 'Bernhard is a rhino' or 'Sandra got the football' but not both then Mary left the football. It is impossible that if 'Bernhard is a rhino' or 'Jeff put down the milk' or both then John went to the office.
It is likely that either 'Jeff put down the milk' or 'Greg is a lion' but not both.
It is unlikely that either 'Jeff put down the milk' or 'Greg is a lion' but not both.
It is likely that either 'Jeff put down the milk' or 'Greg is a lion' 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
  1.0::factA.
  0.1::factB.
  0.05::factC.
  %hop1
  0.1::factX:-or(factA,factB).
  0.5::factY:-xor(factC,factA).
  0.0::factZ:-or(factC,factB).

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

  query(conclusion).
  
Either 'Jeff put down the milk' or 'Greg is a lion' but not both.