Blogger Comments:
[1] To be clear, because cohesive relations are non-structural, it is theoretically inconsistent to include them in a model of structure types.
[2] To be clear, Martin's (1992) systems of IDENTIFICATION and IDEATION are rebrandings of Halliday & Hasan's (1976) systems of REFERENCE and LEXICAL COHESION relocated from lexicogrammar to discourse semantics. Evidence here.
[3] Importantly, before 1992, Lemke had already recanted his view that 'covariate' was a type of structure. Lemke (1988: 159):
My own 'covariate structure' (Lemke 1985), which includes Halliday's univariate type, is for the case of homogeneous relations of co-classed units, and should perhaps be called a 'structuring principle' rather than a kind of structure.