The question can also be asked from the perspective of recognition and from the perspective of generation. There is the structure that the speaker puts there and the structure the hearer discovers there. Are these the same? Does one have primacy over the other? For example, does the speaker impose the structure so that it is the job of the hearer to discover it, no matter what it is, or is it necessary for the speaker to design his discourse in a way that makes it as easy as possible for the hearer to interpret?