context: Chances are about even that Fred dropped the milk. It is highly likely that Mary went to the kitchen. There is almost no chance that John put down the apple.
hypothesis: There is almost no chance that either 'Mary went to the kitchen' or 'John put down the apple' but not both.
valid_hypothesis: It is highly likely that either 'Mary went to the kitchen' or 'John put down the apple' but not both.
invalid_hypothesis: There is almost no chance that either 'Mary went to the kitchen' or 'John put down the apple' 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.
    0.9::factB.
    0.02::factC.
    
  
    %hop2
    conclusion:-xor(factB,factC).
  
    query(conclusion).
    
hypothesis_assertion: Either 'Mary went to the kitchen' or 'John put down the apple' but not both.