Exchange structure 69However, perhaps the most important modifications we now propose arise
from a more rigorous application of the principles underlying the formulation
of rank-scale descriptions. In the original description the structure of exchanges
was expressed in terms of three elements I(nitiation), R(esponse) and F(eedback)
and the summary formula for all exchanges I(R)(F) indicated that all well-
formed exchanges consisted minimally of two and maximally of three elements.
In addition, fully aware of Halliday’s arguments in favour of ‘double
labelling’, which we rehearsed above (p. 57), Sinclair and Coulthard set up
three classes of move, opening, answering and follow-up, to label those
units which realized the elements of structure IRF.
Sinclair and Coulthard proposed five major classes of exchange and labelled
them, for ease of reference, according to the class of act realizing the head
of the opening move and according to whether it was a teacher or a pupil
who uttered it. We present below the structure and then an analysed example
of each of five classes of exchange.
I with elicit as head
1 Teacher eliciting exchange: Structure R with reply as head
F with evaluation as head
Example:
I: What’s the name of this cutter?
R: Hacksaw
F: The hacksaw
I with directive as head
2 Teacher directing exchange: Structure R with react as head
(F) with evaluation as head
Example:
I: I want you to take your pen and I want you to rub it as hard as you
can on something woollen
R: Activity
F: None
I with inform as head
3 Teacher informing exchange: Structure R with acknowledge as
head
Example:
I: Luckily, the French could read Greek
R: Non-verbal Acknowledgement
I with elicit as head
4 Pupil eliciting exchange: Structure
R with reply as head
Example:
I: Are the numbers for le—for the letters?
R: Yes