context: It is probable that Julius is gray. It is impossible that Mary went to the office. We believe that John moved to the garden.
hypothesis: We believe that either 'Mary went to the office' or 'John moved to the garden' but not both.
valid_hypothesis: We believe that either 'Mary went to the office' or 'John moved to the garden' but not both.
invalid_hypothesis: Chances are slight that either 'Mary went to the office' or 'John moved to the garden' 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.
    0.0::factB.
    0.75::factC.
    
  
    %hop2
    conclusion:-xor(factB,factC).
  
    query(conclusion).
    
hypothesis_assertion: Either 'Mary went to the office' or 'John moved to the garden' but not both.