We believe that Brian is white. It is almost certain that Lily is a swan. It is probably not the case that Bernhard is white. It is certain that if 'Brian is white' or 'Lily is a swan' or both then Mary went to the hallway. It is certain that if 'Bernhard is white and Lily is a swan' then John got the milk. Chances are about even that if 'Bernhard is white and Lily is a swan' then Emily is a wolf.
It is highly likely that either 'Mary went to the hallway' or 'Emily is a wolf' but not both.
It is highly likely that either 'Mary went to the hallway' or 'Emily is a wolf' but not both.
It is improbable that either 'Mary went to the hallway' or 'Emily is a wolf' 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.
  0.95::factB.
  0.25::factC.
  %hop1
  1.0::factX:-or(factA,factB).
  1.0::factY:-and(factC,factB).
  0.5::factZ:-and(factC,factB).

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

  query(conclusion).
  
Either 'Mary went to the hallway' or 'Emily is a wolf' but not both.