There is a better than even chance that Greg is yellow. It is probably the case that Bernhard is white. It is highly likely that Julius is a swan. It is unlikely that if 'Greg is yellow and Bernhard is white' then Mary moved to the garden. We believe that if either 'Bernhard is white' or 'Julius is a swan' but not both then Lily is a lion. It is probably the case that if 'Bernhard is white' or 'Greg is yellow' or both then Sandra left the apple.
It is certain that either 'Greg is yellow' or 'Lily is a lion' but not both.
Chances are about even that either 'Greg is yellow' or 'Lily is a lion' but not both.
It is certain that either 'Greg is yellow' or 'Lily is a lion' 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
  0.6::factA.
  0.7::factB.
  0.9::factC.
  %hop1
  0.2::factX:-and(factA,factB).
  0.75::factY:-xor(factB,factC).
  0.7::factZ:-or(factB,factA).

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

  query(conclusion).
  
Either 'Greg is yellow' or 'Lily is a lion' but not both.