It is likely that Mary is in the bathroom. There is little chance that Jeff left the apple. It is likely that John moved to the garden. It is almost certain that if 'Jeff left the apple and John moved to the garden' then Brian is a swan. We believe that if 'Mary is in the bathroom' or 'John moved to the garden' or both then Lily is white. It is highly unlikely that if 'Jeff left the apple' or 'John moved to the garden' or both then Greg is a lion.
It is likely that either 'Jeff left the apple' or 'John moved to the garden' but not both.
It is likely that either 'Jeff left the apple' or 'John moved to the garden' but not both.
It is probably not the case that either 'Jeff left the apple' or 'John moved to the garden' 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.
  0.1::factB.
  0.7::factC.
  %hop1
  0.95::factX:-and(factB,factC).
  0.75::factY:-or(factA,factC).
  0.05::factZ:-or(factB,factC).

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

  query(conclusion).
  
Either 'Jeff left the apple' or 'John moved to the garden' but not both.