It is impossible that Greg is a swan. There is almost no chance that Lily is yellow. There is a better than even chance that Bernhard is white. Chances are slight that if either 'Lily is yellow' or 'Bernhard is white' but not both then Julius is a frog. It is impossible that if 'Bernhard is white' or 'Greg is a swan' or both then Mary got the football. There is little chance that if either 'Lily is yellow' or 'Greg is a swan' but not both then John discarded the milk.
Chances are slight that either 'Julius is a frog' or 'Lily is yellow' but not both.
Chances are slight that either 'Julius is a frog' or 'Lily is yellow' but not both.
There is a better than even chance that either 'Julius is a frog' or 'Lily is yellow' 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
  0.0::factA.
  0.02::factB.
  0.6::factC.
  %hop1
  0.1::factX:-xor(factB,factC).
  0.0::factY:-or(factC,factA).
  0.1::factZ:-xor(factB,factA).

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

  query(conclusion).
  
Either 'Julius is a frog' or 'Lily is yellow' but not both.