It is certain that Sumit is tired. We believe that Brian is a lion. It is almost certain that John went to the office. There is a better than even chance that if either 'John went to the office' or 'Sumit is tired' but not both then Bernhard is a swan. It is improbable that if 'Brian is a lion and John went to the office' then Julius is yellow. It is likely that if 'Brian is a lion and John went to the office' then Mary dropped the apple.
It is certain that either 'John went to the office' or 'Bernhard is a swan' but not both.
It is certain that either 'John went to the office' or 'Bernhard is a swan' but not both.
It is probably not the case that either 'John went to the office' or 'Bernhard is a swan' 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
  1.0::factA.
  0.75::factB.
  0.95::factC.
  %hop1
  0.6::factX:-xor(factC,factA).
  0.1::factY:-and(factB,factC).
  0.7::factZ:-and(factB,factC).

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

  query(conclusion).
  
Either 'John went to the office' or 'Bernhard is a swan' but not both.