There is almost no chance that Lily is a frog. It is probably not the case that Daniel put down the milk. There is little chance that Greg is green. We believe that if 'Greg is green and Lily is a frog' then Mary moved to the garden. It is probably not the case that if 'Greg is green' or 'Lily is a frog' or both then Emily is a mouse. It is certain that if either 'Lily is a frog' or 'Greg is green' but not both then John discarded the apple.
There is a better than even chance that either 'Greg is green' or 'Lily is a frog' but not both.
Chances are slight that either 'Greg is green' or 'Lily is a frog' but not both.
There is a better than even chance that either 'Greg is green' or 'Lily is a frog' 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.
  0.25::factB.
  0.1::factC.
  %hop1
  0.75::factX:-and(factC,factA).
  0.25::factY:-or(factC,factA).
  1.0::factZ:-xor(factA,factC).

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

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