context: There is a better than even chance that John got the apple. We doubt that Bernhard is white. It is highly likely that Greg is gray. It is likely that if 'Bernhard is white' or 'John got the apple' or both then Jessica is a cat. It is probably the case that if 'John got the apple and Greg is gray' then Julius is a lion. There is a better than even chance that if either 'Greg is gray' or 'John got the apple' but not both then Brian is a frog.
hypothesis: It is impossible that 'Julius is a lion and Greg is gray'.
valid_hypothesis: Chances are about even that 'Julius is a lion and Greg is gray'.
invalid_hypothesis: It is impossible that 'Julius is a lion and Greg is gray'.
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
    0.6::factA.
    0.2::factB.
    0.9::factC.
    %hop1
    0.7::factX:-or(factB,factA).
    0.7::factY:-and(factA,factC).
    0.6::factZ:-xor(factC,factA).
  
    %hop2
    conclusion:-and(factY,factC).
  
    query(conclusion).
    
hypothesis_assertion: 'Julius is a lion and Greg is gray'.