We doubt that Sandra got the football. Chances are about even that Lily is a swan. It is almost certain that Brian is white. It is highly likely that if 'Sandra got the football' or 'Lily is a swan' or both then Mary moved to the office. It is highly likely that if 'Lily is a swan' or 'Sandra got the football' or both then Bernhard is green. It is likely that if 'Lily is a swan' or 'Brian is white' or both then Greg is a lion.
Chances are slight that either 'Lily is a swan' or 'Mary moved to the office' but not both.
Chances are slight that either 'Lily is a swan' or 'Mary moved to the office' but not both.
We believe that either 'Lily is a swan' or 'Mary moved 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
  0.2::factA.
  0.5::factB.
  0.95::factC.
  %hop1
  0.9::factX:-or(factA,factB).
  0.9::factY:-or(factB,factA).
  0.7::factZ:-or(factB,factC).

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

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