context: It is likely that Bernhard is a rhino. It is impossible that Julius is yellow. There is little chance that Greg is a swan.
hypothesis: It is likely that either 'Bernhard is a rhino' or 'Greg is a swan' but not both.
valid_hypothesis: It is likely that either 'Bernhard is a rhino' or 'Greg is a swan' but not both.
invalid_hypothesis: It is unlikely that either 'Bernhard is a rhino' or 'Greg is a swan' 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.
    0.1::factC.
    
  
    %hop2
    conclusion:-xor(factA,factC).
  
    query(conclusion).
    
hypothesis_assertion: Either 'Bernhard is a rhino' or 'Greg is a swan' but not both.