context: It is improbable that Lily is gray. Chances are slight that Jeff dropped the apple. We doubt that John got the milk. Chances are about even that if 'John got the milk' or 'Lily is gray' or both then Gertrude is a mouse. There is a very good chance that if either 'Jeff dropped the apple' or 'John got the milk' but not both then Mary went to the hallway. We believe that if either 'John got the milk' or 'Jeff dropped the apple' but not both then Sandra left the football.
hypothesis: It is almost certain that 'Lily is gray' or 'Jeff dropped the apple' or both.
valid_hypothesis: It is unlikely that 'Lily is gray' or 'Jeff dropped the apple' or both.
invalid_hypothesis: It is almost certain that 'Lily is gray' or 'Jeff dropped the apple' or 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
    0.1::factA.
    0.1::factB.
    0.2::factC.
    %hop1
    0.5::factX:-or(factC,factA).
    0.8::factY:-xor(factB,factC).
    0.75::factZ:-xor(factC,factB).
  
    %hop2
    conclusion:-or(factA,factB).
  
    query(conclusion).
    
hypothesis_assertion: 'Lily is gray' or 'Jeff dropped the apple' or both.