context: We believe that John got the football. It is highly unlikely that Greg is a swan. It is certain that Lily is yellow. It is likely that if either 'John got the football' or 'Greg is a swan' but not both then Jason is thirsty. There is almost no chance that if 'Greg is a swan and Lily is yellow' then Brian is a lion. We doubt that if 'John got the football' or 'Greg is a swan' or both then Gertrude is a sheep.
hypothesis: It is probably not the case that either 'John got the football' or 'Lily is yellow' but not both.
valid_hypothesis: It is probably not the case that either 'John got the football' or 'Lily is yellow' but not both.
invalid_hypothesis: It is likely that either 'John got the football' or 'Lily 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
    0.75::factA.
    0.05::factB.
    1.0::factC.
    %hop1
    0.7::factX:-xor(factA,factB).
    0.02::factY:-and(factB,factC).
    0.2::factZ:-or(factA,factB).
  
    %hop2
    conclusion:-xor(factA,factC).
  
    query(conclusion).
    
hypothesis_assertion: Either 'John got the football' or 'Lily is yellow' but not both.