There is a very good chance that John got the apple. It is probable that Greg is white. We doubt that Julius is a swan. It is almost certain that if 'John got the apple' or 'Julius is a swan' or both then Sandra took the football. There is little chance that if 'Greg is white' or 'Julius is a swan' or both then Brian is gray. It is probably the case that if 'John got the apple and Greg is white' then Lily is a rhino.
It is probably not the case that either 'Julius is a swan' or 'Brian is gray' but not both.
It is probably not the case that either 'Julius is a swan' or 'Brian is gray' but not both.
It is almost certain that either 'Julius is a swan' or 'Brian 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
  0.8::factA.
  0.7::factB.
  0.2::factC.
  %hop1
  0.95::factX:-or(factA,factC).
  0.1::factY:-or(factB,factC).
  0.7::factZ:-and(factA,factB).

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

  query(conclusion).
  
Either 'Julius is a swan' or 'Brian is gray' but not both.