This is an interesting perspective, since by now I'm pretty used to filtering the meaning of a document by the communicative purpose(s). This, I think, is where the differences between genre studies / systemic functional linguistics and the perspective of the author of this text become more apparent t me. (This is Marta)

This is an interesting area to me (again, coming from genre studies) because some elements for a given genre of document are obligatory and others aren't. An image of the completed dish isn't obligatory for a recipe, but ingredients and steps to make the dish are (if you have a list of just ingredients, that's a shopping list or maybe a vocab list for a language classroom, but not a recipe!). (This is Marta)

This makes me think of what I learnt in genre studies (which relates to systemic functional linguistics): the idea of texts (including documents) having repeating contexts in which they occur that relate to their communicative purpose (for example, the communicative purpose of a wedding invitation is to give you info about wedding time / place / etc. in hopes that you'll attend; this is repeating because all wedding invitations have that purpose). Diving into the works of authors within this part of applied linguistics, like Michael Halliday, could be used to help flesh out understanding of this topic from a slightly different perspective. (this is Marta)