context: It is certain that Greg is white. It is highly unlikely that John got the milk. We doubt that Lily is a rhino.
hypothesis: It is almost certain that either 'John got the milk' or 'Greg is white' but not both.
valid_hypothesis: It is almost certain that either 'John got the milk' or 'Greg is white' but not both.
invalid_hypothesis: We doubt that either 'John got the milk' or 'Greg is white' 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
    1.0::factA.
    0.05::factB.
    0.2::factC.
    
  
    %hop2
    conclusion:-xor(factB,factA).
  
    query(conclusion).
    
hypothesis_assertion: Either 'John got the milk' or 'Greg is white' but not both.