context: It is probably not the case that Brian is a swan. There is almost no chance that Greg is a frog. It is certain that Bernhard is yellow. It is impossible that if 'Brian is a swan' or 'Bernhard is yellow' or both then Mary left the milk. It is likely that if either 'Greg is a frog' or 'Bernhard is yellow' but not both then Julius is white. It is probable that if 'Bernhard is yellow and Brian is a swan' then John went to the kitchen.
hypothesis: There is almost no chance that 'Mary left the milk' or 'Greg is a frog' or both.
valid_hypothesis: There is almost no chance that 'Mary left the milk' or 'Greg is a frog' or both.
invalid_hypothesis: It is certain that 'Mary left the milk' or 'Greg is a frog' 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
    0.25::factA.
    0.02::factB.
    1.0::factC.
    %hop1
    0.0::factX:-or(factA,factC).
    0.7::factY:-xor(factB,factC).
    0.7::factZ:-and(factC,factA).
  
    %hop2
    conclusion:-or(factX,factB).
  
    query(conclusion).
    
hypothesis_assertion: 'Mary left the milk' or 'Greg is a frog' or both.