context: It is unlikely that Winona is a wolf. Chances are slight that Brian is a swan. It is probably the case that Bernhard is a frog. We believe that if 'Brian is a swan' or 'Bernhard is a frog' or both then Jason is tired. It is certain that if 'Brian is a swan and Bernhard is a frog' then Mary left the football. It is improbable that if 'Brian is a swan' or 'Winona is a wolf' or both then John got the milk.
hypothesis: We doubt that 'Winona is a wolf' or 'John got the milk' or both.
valid_hypothesis: We doubt that 'Winona is a wolf' or 'John got the milk' or both.
invalid_hypothesis: It is likely that 'Winona is a wolf' or 'John got the milk' 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
    0.2::factA.
    0.1::factB.
    0.7::factC.
    %hop1
    0.75::factX:-or(factB,factC).
    1.0::factY:-and(factB,factC).
    0.1::factZ:-or(factB,factA).
  
    %hop2
    conclusion:-or(factA,factZ).
  
    query(conclusion).
    
hypothesis_assertion: 'Winona is a wolf' or 'John got the milk' or both.