Martin (1992: 235):
The Hartford school modelled conjunctive relations between actions, more or less equivalent to the TRANSITIVITY function Process in systemic theory. Since TRANSITIVITY relations are treated as part of lexicogrammar in the model developed here, an appropriate discourse semantics unit needs to be found. The unit message will be adopted here, where this is realised as a ranking clause that is neither a projection, nor a hypotactically dependent elaborating clause. This means that locutions and ideas, elaborating beta clauses and all embedded clauses will be treated as part of messages rather than as conjunctively related units in their own right.
 In SFL theory, transitivity is a system of the experiential metafunction. A consistent discourse semantics unit with 'transitivity relations' would therefore be an experiential unit. Here, however, it is a logical discourse semantics unit that is deemed 'appropriate'. In the grammar, it is the rank units (forms) that are logically related in complexes.
 In SFL theory, the term 'message' is already used for a unit of the textual metafunction on the semantic stratum, and it is (groups of) messages that are conjoined by cohesive conjunction. Here it is used for units related by conjunction, but, as conjunction is misconstrued as logical and structural, it is misconstrued as a unit of logical structure. That is, although textual meaning has been misconstrued here as logical, the textual term has been retained, thereby creating a further theoretical inconsistency — cf 'clause as message', the thematic (textual) structure of the clause.
 In SFL theory, there are two major types of logical relations: expansion and projection. The second of these major types, projection, is thus not included as a logical relation at the level of discourse semantics.
Similarly, within expansion, there are three major types: elaboration, extension and enhancement. The first of these major types, elaboration, is thus not included as a logical relation at the level of discourse semantics — if the interdependency relation is hypotactic.
Excluding both major logical relations has serious ramifications for considerations of the distinction between congruent and incongruent stratal relations in determining grammatical metaphor.
The absence of projection follows from the rebranding of cohesive conjunction, which is the deployment of (only) expansion relations by the textual metafunction at the stratum of lexicogrammar, as the logical dimension of a higher stratum: discourse semantics.
On the other hand, in the discourse semantic model, types of elaboration are variously misconstrued as types of extension or enhancement, as demonstrated in earlier posts.