context: It is certain that Bernhard is a swan. It is highly likely that Julius is a rhino. There is little chance that Fred dropped the apple. There is a very good chance that if either 'Julius is a rhino' or 'Fred dropped the apple' but not both then John went to the hallway. It is improbable that if 'Julius is a rhino' or 'Fred dropped the apple' or both then Lily is green. It is probably not the case that if 'Bernhard is a swan' or 'Fred dropped the apple' or both then Brian is yellow.
hypothesis: It is likely that either 'Julius is a rhino' or 'Brian is yellow' but not both.
valid_hypothesis: It is likely that either 'Julius is a rhino' or 'Brian is yellow' but not both.
invalid_hypothesis: It is probably not the case that either 'Julius is a rhino' or 'Brian is yellow' 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.
    0.9::factB.
    0.1::factC.
    %hop1
    0.8::factX:-xor(factB,factC).
    0.1::factY:-or(factB,factC).
    0.25::factZ:-or(factA,factC).
  
    %hop2
    conclusion:-xor(factB,factZ).
  
    query(conclusion).
    
hypothesis_assertion: Either 'Julius is a rhino' or 'Brian is yellow' but not both.