context: We believe that Daniel dropped the apple. It is certain that Greg is a frog. It is highly likely that Lily is a rhino. It is likely that if 'Greg is a frog and Daniel dropped the apple' then Mary got the football. We doubt that if 'Daniel dropped the apple' or 'Greg is a frog' or both then John left the milk. We doubt that if 'Lily is a rhino and Daniel dropped the apple' then Bernhard is a frog.
hypothesis: There is almost no chance that either 'Daniel dropped the apple' or 'Bernhard is a frog' but not both.
valid_hypothesis: There is a better than even chance that either 'Daniel dropped the apple' or 'Bernhard is a frog' but not both.
invalid_hypothesis: There is almost no chance that either 'Daniel dropped the apple' or 'Bernhard 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
    0.75::factA.
    1.0::factB.
    0.9::factC.
    %hop1
    0.7::factX:-and(factB,factA).
    0.2::factY:-or(factA,factB).
    0.2::factZ:-and(factC,factA).
  
    %hop2
    conclusion:-xor(factA,factZ).
  
    query(conclusion).
    
hypothesis_assertion: Either 'Daniel dropped the apple' or 'Bernhard is a frog' but not both.