context: Chances are slight that Mary left the apple. It is likely that Bernhard is gray. We believe that Julius is a rhino. It is certain that if either 'Bernhard is gray' or 'Mary left the apple' but not both then Winona is a sheep. It is probably the case that if 'Julius is a rhino and Bernhard is gray' then Brian is a frog. There is almost no chance that if 'Mary left the apple and Bernhard is gray' then John got the milk.
hypothesis: We believe that 'Mary left the apple' or 'Winona is a sheep' or both.
valid_hypothesis: We believe that 'Mary left the apple' or 'Winona is a sheep' or both.
invalid_hypothesis: It is unlikely that 'Mary left the apple' or 'Winona is a sheep' or 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.
    0.7::factB.
    0.75::factC.
    %hop1
    1.0::factX:-xor(factB,factA).
    0.7::factY:-and(factC,factB).
    0.02::factZ:-and(factA,factB).
  
    %hop2
    conclusion:-or(factA,factX).
  
    query(conclusion).
    
hypothesis_assertion: 'Mary left the apple' or 'Winona is a sheep' or both.