context: Chances are about even that Sandra is in the kitchen. There is almost no chance that Bernhard is a frog. It is likely that Gertrude is a sheep. We doubt that if 'Gertrude is a sheep and Bernhard is a frog' then Lily is a lion. It is unlikely that if 'Bernhard is a frog and Gertrude is a sheep' then John went to the garden. It is almost certain that if 'Sandra is in the kitchen and Gertrude is a sheep' then Julius is gray.
hypothesis: There is almost no chance that either 'Bernhard is a frog' or 'Lily is a lion' but not both.
valid_hypothesis: There is almost no chance that either 'Bernhard is a frog' or 'Lily is a lion' but not both.
invalid_hypothesis: It is likely that either 'Bernhard is a frog' or 'Lily is a lion' 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
    0.5::factA.
    0.02::factB.
    0.7::factC.
    %hop1
    0.2::factX:-and(factC,factB).
    0.2::factY:-and(factB,factC).
    0.95::factZ:-and(factA,factC).
  
    %hop2
    conclusion:-xor(factB,factX).
  
    query(conclusion).
    
hypothesis_assertion: Either 'Bernhard is a frog' or 'Lily is a lion' but not both.