context: We believe that Jeff went to the bedroom. It is unlikely that Julius is gray. There is a better than even chance that Greg is white.
hypothesis: It is probably the case that either 'Julius is gray' or 'Jeff went to the bedroom' but not both.
valid_hypothesis: It is probably the case that either 'Julius is gray' or 'Jeff went to the bedroom' but not both.
invalid_hypothesis: There is almost no chance that either 'Julius is gray' or 'Jeff went to the bedroom' 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
    0.75::factA.
    0.2::factB.
    0.6::factC.
    
  
    %hop2
    conclusion:-xor(factB,factA).
  
    query(conclusion).
    
hypothesis_assertion: Either 'Julius is gray' or 'Jeff went to the bedroom' but not both.