It is improbable that Sandra got the football. We doubt that Yann is bored. It is improbable that Mary went to the office. We believe that if either 'Yann is bored' or 'Mary went to the office' but not both then Bernhard is white. It is impossible that if either 'Sandra got the football' or 'Mary went to the office' but not both then Lily is white. There is almost no chance that if 'Mary went to the office' or 'Yann is bored' or both then Greg is a swan.
We doubt that either 'Bernhard is white' or 'Mary went to the office' but not both.
We doubt that either 'Bernhard is white' or 'Mary went to the office' but not both.
It is certain that either 'Bernhard is white' or 'Mary went to the office' 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.
  0.1::factC.
  %hop1
  0.75::factX:-xor(factB,factC).
  0.0::factY:-xor(factA,factC).
  0.02::factZ:-or(factC,factB).

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

  query(conclusion).
  
Either 'Bernhard is white' or 'Mary went to the office' but not both.