context: It is highly unlikely that Bernhard is a swan. It is impossible that Julius is a swan. We doubt that John moved to the garden. It is probably the case that if 'Bernhard is a swan' or 'John moved to the garden' or both then Lily is white. It is impossible that if 'Bernhard is a swan' or 'John moved to the garden' or both then Mary dropped the apple. It is likely that if 'Bernhard is a swan and John moved to the garden' then Greg is a frog.
hypothesis: It is impossible that 'Greg is a frog and Mary dropped the apple'.
valid_hypothesis: It is impossible that 'Greg is a frog and Mary dropped the apple'.
invalid_hypothesis: Chances are about even that 'Greg is a frog and Mary dropped the apple'.
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
    0.05::factA.
    0.0::factB.
    0.2::factC.
    %hop1
    0.7::factX:-or(factA,factC).
    0.0::factY:-or(factA,factC).
    0.7::factZ:-and(factA,factC).
  
    %hop2
    conclusion:-and(factZ,factY).
  
    query(conclusion).
    
hypothesis_assertion: 'Greg is a frog and Mary dropped the apple'.