The seminal work on discourse analysis was carried out in classrooms, and it is from this that an understanding of structure of the exchanges that make up spoken discourse is drawn. Sinclair and Couithaerd (1975) identified three levels of discourse: the exchange, a turn-taking interactional sequence; the move, or contribution of a participant to the exchange in a turn; and the act, identifiable within the move and playing a specific linguistic function such as questioning or instructing. The three-part exchange teacher initiation / student response / teacher feedback (IRF) was proposed as the basic unit of classroom interaction, since referred to by Lemke (1985,1990) as dialogue. Mehan (1988, p.121) describes what are arguably features of classroom speech genre:
The instructional phase ... is composed of characteristic interactional sequences. This exchange of academic information in interactional units is called 'elicitation sequences.' These units are interactional in that they are a joint production of teacher and student; they are sequential in that they occur one after the other in interaction.
These sequences have three interconnected parts: an initiation act, a reply act, and evaluation act.
Students and teachers share an understanding of the social situation in terms of appropriate discourse and accompanying behaviour, i.e. teachers and students come together in classrooms knowing that certain types of interaction - including the IRF sequence - are appropriate in the situation, and it is their role to participate using the register of the classroom. The IRF sequence is generally equated with exchanges where the teacher is responsible for the initiation of interaction with the aim of eliciting 'information' ,and the exchange is continued, possibly "though extended sequences until the raply called for is obtained" (Mehan, 1988 ,p.127). However , IRF sequences can be initiated by students, and it can be argued that at...