This article deals with English tag questions demanding knowledge or action. Conversationally, these are rather recognizable functions in that they project specific expected responses and involve linguistically construed interactional roles. We focus on these tag questions to compare two analytical models developed within Systemic-Functional linguistics: the speech function model (Halliday & Matthiessen 2004) and the exchange structure analysis (Berry 1981a(Berry , 1981b(Berry , 1981c(Berry , 2016. In this comparison, we address the following questions. Which conversational properties and form-function correlations do the models focus on? What aspects of their functioning in discourse do they reveal? Ultimately our detailed corpus-driven analysis of tag questions which incorporates grammatical, prosodic and semantic factors suggests that both approaches have their strengths and weaknesses. We argue for a synthesis between both approaches and conclude that further development of the principles of adjacency and exchange shows potential for greater understanding of formfunction relations in grammatical constructions such as tag questions. . In Section 5 we compare the two approaches, answering questions such as the following: Which aspects of spontaneous dialogue are captured better by speech function analysis and which by exchange analysis? Can the two be combined? What issues and elements need to be further developed?
Data and data analysis