 From a structured question meaning it is always possible to obtain the corresponding proposition set meaning, by applying \(B\) to all the elements of \(R\) (and taking the downward closure of the resulting set of propositions in case we want an inquisitive question meaning in the sense of \(\Inq_B\). It is not possible to go in the other direction, which means that structured question meanings have strictly more expressive power than proposition set meanings (e.g., von Stechow 1991, Krifka 2001). 