context: It is certain that Greg is a rhino. We believe that Winona is a cat. It is improbable that Brian is yellow. It is probable that if 'Winona is a cat' or 'Greg is a rhino' or both then Julius is a swan. There is a better than even chance that if either 'Greg is a rhino' or 'Winona is a cat' but not both then Mary took the milk. It is impossible that if either 'Brian is yellow' or 'Greg is a rhino' but not both then Bernhard is a swan.
hypothesis: It is likely that either 'Brian is yellow' or 'Mary took the milk' but not both.
valid_hypothesis: We doubt that either 'Brian is yellow' or 'Mary took the milk' but not both.
invalid_hypothesis: It is likely that either 'Brian is yellow' or 'Mary took 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
    1.0::factA.
    0.75::factB.
    0.1::factC.
    %hop1
    0.7::factX:-or(factB,factA).
    0.6::factY:-xor(factA,factB).
    0.0::factZ:-xor(factC,factA).
  
    %hop2
    conclusion:-xor(factC,factY).
  
    query(conclusion).
    
hypothesis_assertion: Either 'Brian is yellow' or 'Mary took the milk' but not both.