Abstract
Sentences containing pronouns and indefinite noun phrases can be said toexpress open propositions, propositions which display gaps to be filled.This paper addresses the question what is the linguistic content ofthese expressions, what information they can be said to provide to ahearer, and in what sense the information of a speaker can be said tosupport their utterance. We present and motivate first order notions ofcontent, update and support. The three notions are each defined in acompositional fashion and brought together within a single and coherentframework.