There is almost no chance that Sandra got the football. Chances are slight that Brian is a swan. Chances are slight that Bernhard is gray. It is unlikely that if either 'Brian is a swan' or 'Sandra got the football' but not both then Mary left the milk. It is probable that if 'Sandra got the football' or 'Brian is a swan' or both then John dropped the apple. We believe that if either 'Brian is a swan' or 'Sandra got the football' but not both then Julius is white.
It is highly unlikely that 'Brian is a swan and Julius is white'.
It is highly unlikely that 'Brian is a swan and Julius is white'.
It is likely that 'Brian is a swan and Julius is white'.

  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.
  0.1::factB.
  0.1::factC.
  %hop1
  0.2::factX:-xor(factB,factA).
  0.7::factY:-or(factA,factB).
  0.75::factZ:-xor(factB,factA).

  %hop2
  conclusion:-and(factB,factZ).

  query(conclusion).
  
'Brian is a swan and Julius is white'.