Martin (1992: 25):
Following Lemke (1985) [Ideology, Intertextuality and the Notion of Register], discourse semantic structures of this kind will be referred to as covariate. Covariate structures are those in which a semantic interdependency is constructed between items (which may or may not be grammaticalised) and in which dependent items have the potential to themselves be depended on. These structures are the principle resource used by the discourse semantics for constructing text (although multivariate and univariate structures are also found…). … In this model, covariate structures in which one item presumes another are referred to phoric; covariate structures in which information is not so presumed are referred to as expectant.
 Lemke (1988: 159) reinterprets his 'covariate structure' as a structuring principle, rather than a kind of structure:
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.
Martin includes Lemke (1988) in his list of references (p603).
 No argument has been offered to demonstrate that these discourse semantic 'structures' are structures. It has been presumed throughout. This is the logical fallacy known as 'begging the question':
The fallacy of petitio principii, or begging the question, is committed when a proposition which requires proof is assumed without proof.
 Interdependency is a system of the logical metafunction. Here it is applied to systems of the textual metafunction — cohesion — which Martin reconstrues as the full range of metafunctions at a higher level of symbolic abstraction — discourse semantics. Each move creates a serious theoretical inconsistency.
A related inconsistency is the reconstrual of the interdependency relations, hypotaxis and parataxis, as the relations 'presumption' and 'expectancy', respectively, neither of which is a form of interdependency.
 In SFL, the resource for 'constructing text' is the textual metafunction, structural and non-structural, operating at all strata. It is not restricted to one level of symbolic abstraction — 'discourse semantics' — nor is it the concern of the other metafunctions. The interpersonal metafunction is concerned with enacting the self and relationships as meaning; the ideational metafunction is concerned with construing experience as meaning.
 Here a relation that has been explored through the lens of the logical metafunction — as hypotaxis — is given a label of a resource of the textual metafunction — phoric (reference) — and then proposed as a structural principle across all metafunctions at a level of symbolic abstraction above the lexicogrammar — discourse semantics. Each move creates a serious theoretical inconsistency.