Im not sure where a form/function duality would fit in SFL theory.
Blogger Comment:
It fits, for example, in the rank scale. The rank scale is a compositional scale of forms. The unit of each rank is a configuration of functional elements, each of which is realised by a unit of the rank below (except in the case of rank-shift). For example, elements of the function structure of a clause are realised in the form of groups and phrases.
