It is impossible that Julius is gray. It is certain that John went to the office. It is probably not the case that Mary got the football. It is improbable that if 'Mary got the football' or 'Julius is gray' or both then Brian is green. We believe that if 'Julius is gray' or 'Mary got the football' or both then Lily is gray. It is almost certain that if either 'John went to the office' or 'Julius is gray' but not both then Daniel dropped the milk.
There is a very good chance that either 'Brian is green' or 'Lily is gray' but not both.
We doubt that either 'Brian is green' or 'Lily is gray' but not both.
There is a very good chance that either 'Brian is green' or 'Lily is gray' 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
  0.0::factA.
  1.0::factB.
  0.25::factC.
  %hop1
  0.1::factX:-or(factC,factA).
  0.75::factY:-or(factA,factC).
  0.95::factZ:-xor(factB,factA).

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

  query(conclusion).
  
Either 'Brian is green' or 'Lily is gray' but not both.