context: It is unlikely that Gertrude is a sheep. It is improbable that Bernhard is a swan. It is highly unlikely that John went to the hallway. It is probable that if 'Gertrude is a sheep and Bernhard is a swan' then Daniel got the milk. It is highly unlikely that if 'John went to the hallway and Bernhard is a swan' then Greg is a frog. We believe that if either 'Gertrude is a sheep' or 'Bernhard is a swan' but not both then Lily is a rhino.
hypothesis: It is impossible that 'Greg is a frog and Daniel got the milk'.
valid_hypothesis: It is impossible that 'Greg is a frog and Daniel got the milk'.
invalid_hypothesis: Chances are about even that 'Greg is a frog and Daniel got the milk'.
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
    0.2::factA.
    0.1::factB.
    0.05::factC.
    %hop1
    0.7::factX:-and(factA,factB).
    0.05::factY:-and(factC,factB).
    0.75::factZ:-xor(factA,factB).
  
    %hop2
    conclusion:-and(factY,factX).
  
    query(conclusion).
    
hypothesis_assertion: 'Greg is a frog and Daniel got the milk'.