context: There is little chance that John went to the hallway. There is almost no chance that Julius is a swan. There is a very good chance that Mary left the milk. It is highly unlikely that if 'Mary left the milk' or 'John went to the hallway' or both then Bernhard is a swan. It is highly unlikely that if either 'Mary left the milk' or 'Julius is a swan' but not both then Lily is a lion. It is probably the case that if 'John went to the hallway and Julius is a swan' then Brian is a frog.
hypothesis: There is little chance that either 'Mary left the milk' or 'Bernhard is a swan' but not both.
valid_hypothesis: We believe that either 'Mary left the milk' or 'Bernhard is a swan' but not both.
invalid_hypothesis: There is little chance that either 'Mary left the milk' or 'Bernhard 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
    0.1::factA.
    0.02::factB.
    0.8::factC.
    %hop1
    0.05::factX:-or(factC,factA).
    0.05::factY:-xor(factC,factB).
    0.7::factZ:-and(factA,factB).
  
    %hop2
    conclusion:-xor(factC,factX).
  
    query(conclusion).
    
hypothesis_assertion: Either 'Mary left the milk' or 'Bernhard is a swan' but not both.