context: There is almost no chance that Brian is green. It is almost certain that Julius is a lion. It is improbable that Mary dropped the apple. It is probably not the case that if either 'Mary dropped the apple' or 'Brian is green' but not both then Jessica is a sheep. There is almost no chance that if 'Brian is green and Julius is a lion' then Lily is yellow. There is little chance that if 'Julius is a lion' or 'Mary dropped the apple' or both then Bernhard is a frog.
hypothesis: There is a better than even chance that either 'Brian is green' or 'Mary dropped the apple' but not both.
valid_hypothesis: Chances are slight that either 'Brian is green' or 'Mary dropped the apple' but not both.
invalid_hypothesis: There is a better than even chance that either 'Brian is green' or 'Mary dropped the apple' 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
    0.02::factA.
    0.95::factB.
    0.1::factC.
    %hop1
    0.25::factX:-xor(factC,factA).
    0.02::factY:-and(factA,factB).
    0.1::factZ:-or(factB,factC).
  
    %hop2
    conclusion:-xor(factA,factC).
  
    query(conclusion).
    
hypothesis_assertion: Either 'Brian is green' or 'Mary dropped the apple' but not both.