There is almost no chance that John went to the office. It is almost certain that Mary left the football. It is probably the case that Bernhard is a swan. It is unlikely that if 'John went to the office and Bernhard is a swan' then Yann is tired. It is likely that if 'Mary left the football and Bernhard is a swan' then Jessica is a cat. Chances are about even that if 'Bernhard is a swan and Mary left the football' then Daniel took the milk.
It is certain that either 'Bernhard is a swan' or 'Jessica is a cat' but not both.
It is probably not the case that either 'Bernhard is a swan' or 'Jessica is a cat' but not both.
It is certain that either 'Bernhard is a swan' 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
  0.02::factA.
  0.95::factB.
  0.7::factC.
  %hop1
  0.2::factX:-and(factA,factC).
  0.7::factY:-and(factB,factC).
  0.5::factZ:-and(factC,factB).

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

  query(conclusion).
  
Either 'Bernhard is a swan' or 'Jessica is a cat' but not both.