Martin (1992: 56):
In a model of discourse structure such as that proposed by the Birmingham school, all aspects of text structure have to be incorporated into a single rank scale such as act-move-exchange-transaction-lesson. This naturally puts a great deal of pressure on move structure to capture cohesive relations as multivariately structured act sequences. Here on the other hand, identification, conjunction and ideation will be treated separately from negotiation as discourse structures in their own right.
Cohesive relations cannot be "captured" by move structure as multivariately structured act sequences — whatever the pressure — for three reasons.
- First, cohesive relations are not structures, multivariate or otherwise.
- Second, cohesive relations are textual in metafunction, whereas act sequences are presented as interpersonal.
- Third, cohesive relations are lexicogrammatical in terms of level of symbolic abstraction, whereas act sequences are presented as semantic.