We believe that Greg is white. It is probably the case that Gertrude is a mouse. It is almost certain that Lily is green. It is highly likely that if either 'Gertrude is a mouse' or 'Lily is green' but not both then John picked up the apple. We believe that if 'Lily is green and Gertrude is a mouse' then Mary went to the kitchen. It is certain that if 'Gertrude is a mouse' or 'Lily is green' or both then Brian is gray.
We doubt that either 'John picked up the apple' or 'Gertrude is a mouse' but not both.
It is highly likely that either 'John picked up the apple' or 'Gertrude is a mouse' but not both.
We doubt that either 'John picked up the apple' or 'Gertrude is a mouse' 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
  0.75::factA.
  0.7::factB.
  0.95::factC.
  %hop1
  0.9::factX:-xor(factB,factC).
  0.75::factY:-and(factC,factB).
  1.0::factZ:-or(factB,factC).

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

  query(conclusion).
  
Either 'John picked up the apple' or 'Gertrude is a mouse' but not both.