It is probably not the case that Winona is a mouse. There is almost no chance that Lily is a frog. It is unlikely that Greg is yellow. It is highly unlikely that if either 'Winona is a mouse' or 'Greg is yellow' but not both then Mary left the football. It is probably the case that if either 'Lily is a frog' or 'Greg is yellow' but not both then John moved to the office. It is highly likely that if 'Greg is yellow and Winona is a mouse' then Bernhard is a swan.
We believe that either 'John moved to the office' or 'Bernhard is a swan' but not both.
It is improbable that either 'John moved to the office' or 'Bernhard is a swan' but not both.
We believe that either 'John moved 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
  0.25::factA.
  0.02::factB.
  0.2::factC.
  %hop1
  0.05::factX:-xor(factA,factC).
  0.7::factY:-xor(factB,factC).
  0.9::factZ:-and(factC,factA).

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

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