Martin (1992: 505):
Where the models do differ substantively is with respect to Martin's suggestion that there is a network of relationships underlying register which relates text types to each other in ways they cannot be inter-related considered from the perspective of any one register variable.
This misunderstands the SFL model with which Hasan's model is consistent, and with which Martin's model is not consistent.
In SFL theory, registers are text types (genres) viewed from the system pole of the cline of instantiation. Text types realise situation types, whose metafunctional dimensions are field tenor and mode. Text types differ in terms of the contextual features (field tenor and mode) they realise.
In Martin's model, a system of mode is relocated from context (misconstrued as register) to a new higher stratum (misconstrued as genre), with this higher system said to "underlie" the lower stratum.
Moreover, schematic structure — text structure — is located on the higher stratum of "context" (genre), instead of on the stratum of semantics.