context: It is improbable that Bernhard is green. It is almost certain that Julius is white. There is a better than even chance that Mary got the apple. There is little chance that if 'Julius is white' or 'Bernhard is green' or both then Greg is a swan. There is a very good chance that if 'Julius is white' or 'Mary got the apple' or both then Lily is a rhino. It is highly unlikely that if 'Bernhard is green and Mary got the apple' then Fred dropped the milk.
hypothesis: We doubt that either 'Bernhard is green' or 'Greg is a swan' but not both.
valid_hypothesis: We doubt that either 'Bernhard is green' or 'Greg is a swan' but not both.
invalid_hypothesis: It is probably the case that either 'Bernhard is green' 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
    0.1::factA.
    0.95::factB.
    0.6::factC.
    %hop1
    0.1::factX:-or(factB,factA).
    0.8::factY:-or(factB,factC).
    0.05::factZ:-and(factA,factC).
  
    %hop2
    conclusion:-xor(factA,factX).
  
    query(conclusion).
    
hypothesis_assertion: Either 'Bernhard is green' or 'Greg is a swan' but not both.