context: There is little chance that Sandra left the milk. It is probably not the case that John went to the garden. Chances are about even that Bernhard is green.
hypothesis: Chances are about even that either 'Bernhard is green' or 'Sandra left the milk' but not both.
valid_hypothesis: Chances are about even that either 'Bernhard is green' or 'Sandra left the milk' but not both.
invalid_hypothesis: It is impossible that either 'Bernhard is green' or 'Sandra left 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
    0.1::factA.
    0.25::factB.
    0.5::factC.
    
  
    %hop2
    conclusion:-xor(factC,factA).
  
    query(conclusion).
    
hypothesis_assertion: Either 'Bernhard is green' or 'Sandra left the milk' but not both.