context: Chances are about even that Mary is in the hallway. There is a better than even chance that John discarded the milk. We believe that Greg is gray.
hypothesis: It is almost certain that either 'Mary is in the hallway' or 'John discarded the milk' but not both.
valid_hypothesis: Chances are about even that either 'Mary is in the hallway' or 'John discarded the milk' but not both.
invalid_hypothesis: It is almost certain that either 'Mary is in the hallway' or 'John discarded the milk' 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.
    0.6::factB.
    0.75::factC.
    
  
    %hop2
    conclusion:-xor(factA,factB).
  
    query(conclusion).
    
hypothesis_assertion: Either 'Mary is in the hallway' or 'John discarded the milk' but not both.