Chances are slight that Greg is yellow. It is unlikely that Brian is a swan. There is a better than even chance that Mary went to the bedroom. There is a very good chance that if 'Mary went to the bedroom and Greg is yellow' then Julius is gray. It is probably the case that if 'Greg is yellow and Brian is a swan' then Bernhard is white. There is little chance that if 'Brian is a swan and Greg is yellow' then John took the milk.
It is improbable that either 'Mary went to the bedroom' or 'Julius is gray' but not both.
There is a better than even chance that either 'Mary went to the bedroom' or 'Julius is gray' but not both.
It is improbable that either 'Mary went to the bedroom' or 'Julius 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
  0.1::factA.
  0.2::factB.
  0.6::factC.
  %hop1
  0.8::factX:-and(factC,factA).
  0.7::factY:-and(factA,factB).
  0.1::factZ:-and(factB,factA).

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

  query(conclusion).
  
Either 'Mary went to the bedroom' or 'Julius is gray' but not both.