 Another development in the scorekeeping model refines the teleological picture adumbrated above to incorporate Questions, construed (along the lines of Section 2.1) as sets of Propositions. When an interlocutor proffers an assertion that is not met with objections by others in the conversation, the Propositional content of that illocution will enter into common ground. When an interlocutor poses a question that is accepted by others, we may represent the change as an addition to Common Ground of the set of propositions that is the Interrogative content of that illocution. The presence of that Interrogative obliges interlocutors to work to rule all but one Proposition that is a complete answer to the Interrogative. Because Interrogatives stand in inferential relations to one another (Q1 entails Q2 just in case any answer to Q1 is an answer to Q2), one strategy for answering a question is to divide it into tractable questions that it entails: ‘How many covered bridges are there in Japan?’ can be answered by answering that question for each of that country’s 47 prefectures. Roberts (2004, 2012) develops the Question Under Discussion model of conversational dynamics according to which common ground contains a partially ordered set of Interrogatives in addition to a set of Propositions. This teleological approach to conversation bids fair to enrich our understanding of the relations of speech acts to other central topics within pragmatics such as presupposition and  implicature.[18]