Laura Carroll did an excellent job in her “Backpacks vs. Briefcases: Steps Toward Rhetorical Analysis” by creating the triangle of audience, exigence, and constraints. Each item is an important piece to any form of publication, whether it be on paper or on the Internet. These are useful tools that all coincide with one another and create a harmony in whatever you are writing. They reach out to people and in a manner that, in theory, should be positive and assertive.
I find exigence to be the word for the response expected from a certain way of broadcasting a subject. It can be a prediction essentially. For example if you said, “all people are treated equally,” you would probably get a million and one response saying that that is entirely incorrect, most probably from social justice bloggers. But the point being is that exigence is used to get a certain rise out of a certain type of people.
Audience would be those certain types of people that you’re trying to get your words out to. They are the ones you are looking to interest or intrigue with your words and to possibly influence in one way or another with your topic of discussion.
Now constraints are limitations that are set by you or whomever is permitting you to write. These are for keeping one from writing too radically, I believe. If you’re trying to persuade a crowd or inform a mass of people about something you wouldn’t want to put too much pathos in your writing because that could give you superiority complex which would actually end up turning off your audience from listening to you at all.