context: It is probable that Brian is a rhino. It is certain that Mary moved to the office. There is a better than even chance that Greg is a frog.
hypothesis: Chances are about even that either 'Greg is a frog' or 'Brian is a rhino' but not both.
valid_hypothesis: Chances are about even that either 'Greg is a frog' or 'Brian is a rhino' but not both.
invalid_hypothesis: There is almost no chance that either 'Greg is a frog' or 'Brian is a rhino' 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.
    1.0::factB.
    0.6::factC.
    
  
    %hop2
    conclusion:-xor(factC,factA).
  
    query(conclusion).
    
hypothesis_assertion: Either 'Greg is a frog' or 'Brian is a rhino' but not both.