context: Chances are about even that Lily is white. It is likely that Gertrude is a sheep. We doubt that Brian is a lion.
hypothesis: There is a better than even chance that either 'Gertrude is a sheep' or 'Brian is a lion' but not both.
valid_hypothesis: There is a better than even chance that either 'Gertrude is a sheep' or 'Brian is a lion' but not both.
invalid_hypothesis: Chances are slight that either 'Gertrude is a sheep' or 'Brian is a lion' 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.
    0.7::factB.
    0.2::factC.
    
  
    %hop2
    conclusion:-xor(factB,factC).
  
    query(conclusion).
    
hypothesis_assertion: Either 'Gertrude is a sheep' or 'Brian is a lion' but not both.