context: It is probably the case that Julius is a swan. We believe that Bernhard is white. It is probably not the case that John discarded the apple.
hypothesis: It is highly unlikely that either 'Julius is a swan' or 'Bernhard is white' but not both.
valid_hypothesis: Chances are about even that either 'Julius is a swan' or 'Bernhard is white' but not both.
invalid_hypothesis: It is highly unlikely that either 'Julius is a swan' or 'Bernhard is white' 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.
    0.75::factB.
    0.25::factC.
    
  
    %hop2
    conclusion:-xor(factA,factB).
  
    query(conclusion).
    
hypothesis_assertion: Either 'Julius is a swan' or 'Bernhard is white' but not both.