Martin (1992: 202-3):
Consider now a modified version of this part of the interview:
[4:94] a. With the bigger breeds of dog, they're stood on the ground.b. With the smaller breeds such as Dachshunds, they're stood on the table.c. Likewise breeds with similar stature like the Corgis, all the Toy-breeds, and this type of thing are tabled,d. so as the judge can handle them more easily.
This text focusses on similarity as well as difference. Lexical cohesion (the co-hyponymy of Dachshunds with Corgis and Toy-breeds and the repetition of table (table, tabled), comparative reference (similar stature) and an explicit conjunction (likewise) make the comparison clear.
Halliday and Hasan (1976) treat the contrastive relation in [4:94: a–b] as closely related to concession (under the general adversative category) and the similarity in [4:94: b–c] as a kind of additive. Halliday (1985) on the other hand treats contrast as related to additive relations under the heading extension and similarity as closely related to temporals and causals under the heading enhancement. …
These interpretations fail to bring out the very similar ways in which IDENTIFICATION and IDEATION participate in the realisation of both contrast and similarity (as exemplified in [4:84sic] above…
This continues the category error of conflating different (dissimilar) with contrastive (adversative). The logical meaning of dissimilar is N is not like M, whereas the logical meaning of adversative is X and conversely Y. In SFL theory, the logical relation of dissimilar is a subtype of manner, within enhancement, whereas the logical relation of adversative is a subtype of addition, within extension. That is, dissimilar and adversative belong to different major categories within expansion.