context: It is probable that Gertrude is a cat. There is a very good chance that John dropped the milk. It is highly likely that Greg is a rhino.
hypothesis: It is highly unlikely that either 'John dropped the milk' or 'Gertrude is a cat' but not both.
valid_hypothesis: Chances are about even that either 'John dropped the milk' or 'Gertrude is a cat' but not both.
invalid_hypothesis: It is highly unlikely that either 'John dropped the milk' or 'Gertrude is a cat' 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
    0.7::factA.
    0.8::factB.
    0.9::factC.
    
  
    %hop2
    conclusion:-xor(factB,factA).
  
    query(conclusion).
    
hypothesis_assertion: Either 'John dropped the milk' or 'Gertrude is a cat' but not both.