It is certain that Lily is a rhino. It is likely that Jeff left the apple. It is improbable that Greg is gray. There is a better than even chance that if either 'Greg is gray' or 'Jeff left the apple' but not both then Jessica is a cat. It is likely that if 'Greg is gray' or 'Jeff left the apple' or both then Bill went to the office. We doubt that if 'Greg is gray and Lily is a rhino' then Bernhard is a swan.
Chances are about even that either 'Greg is gray' or 'Jessica is a cat' but not both.
Chances are about even that either 'Greg is gray' or 'Jessica is a cat' but not both.
It is certain that either 'Greg is gray' or 'Jessica is a cat' 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.
  0.7::factB.
  0.1::factC.
  %hop1
  0.6::factX:-xor(factC,factB).
  0.7::factY:-or(factC,factB).
  0.2::factZ:-and(factC,factA).

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

  query(conclusion).
  
Either 'Greg is gray' or 'Jessica is a cat' but not both.