context: There is a very good chance that Mary dropped the milk. We doubt that Lily is a swan. It is highly likely that Greg is white. It is highly likely that if either 'Lily is a swan' or 'Greg is white' but not both then Brian is a frog. We believe that if either 'Mary dropped the milk' or 'Lily is a swan' but not both then Bernhard is green. It is highly likely that if either 'Lily is a swan' or 'Mary dropped the milk' but not both then Julius is a rhino.
hypothesis: It is almost certain that either 'Greg is white' or 'Brian is a frog' but not both.
valid_hypothesis: It is probably not the case that either 'Greg is white' or 'Brian is a frog' but not both.
invalid_hypothesis: It is almost certain that either 'Greg is white' or 'Brian is a frog' but not both.
problog: 
    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
    0.8::factA.
    0.2::factB.
    0.9::factC.
    %hop1
    0.9::factX:-xor(factB,factC).
    0.75::factY:-xor(factA,factB).
    0.9::factZ:-xor(factB,factA).
  
    %hop2
    conclusion:-xor(factC,factX).
  
    query(conclusion).
    
hypothesis_assertion: Either 'Greg is white' or 'Brian is a frog' but not both.