context: It is impossible that Sandra left the milk. There is almost no chance that Bernhard is a frog. It is highly likely that Mary moved to the garden. There is little chance that if 'Mary moved to the garden' or 'Sandra left the milk' or both then Lily is a swan. Chances are slight that if 'Mary moved to the garden and Sandra left the milk' then Daniel dropped the apple. There is a very good chance that if 'Sandra left the milk' or 'Bernhard is a frog' or both then Fred is in the office.
hypothesis: It is likely that either 'Bernhard is a frog' or 'Lily is a swan' but not both.
valid_hypothesis: It is improbable that either 'Bernhard is a frog' or 'Lily is a swan' but not both.
invalid_hypothesis: It is likely that either 'Bernhard is a frog' or 'Lily 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
    0.0::factA.
    0.02::factB.
    0.9::factC.
    %hop1
    0.1::factX:-or(factC,factA).
    0.1::factY:-and(factC,factA).
    0.8::factZ:-or(factA,factB).
  
    %hop2
    conclusion:-xor(factB,factX).
  
    query(conclusion).
    
hypothesis_assertion: Either 'Bernhard is a frog' or 'Lily is a swan' but not both.