Martin (1992: 180):
Internal relations in other words structure semiosis; external ones code the structure of the world. A less materialistic interpretation, drawing on the semiotic approach to context to be developed in Chapter 7, could be framed along the following lines. This would treat external relations as by and large oriented to field — they encode the institutional organisation of our culture. Internal relations on the other hand are oriented to genre (including the conversational structure realising genre in dialogic modes) — they encode the organisation of text as it is formulated to construct our culture.
 This is an incorrect reading of the distinction between external and internal conjunctive relations in SFL theory. As cohesive relations, both are text-forming resources of the lexicogrammar that are concerned with marking textual transitions between whole messages or groups of whole messages (Halliday & Matthiessen 2004: 583). External conjunctive relations involve textual relations between 'external phenomena' — that is: between experiences construed as meanings — whereas internal conjunctive relations involve textual relations that are internal to the communication situation itself.
 A materialistic interpretation of internal and external conjunctive relations is thus a misinterpretation, not least because the textual metafunction is concerned with semiotic reality. Halliday & Matthiessen (1999: 398):
The textual metafunction second–order in the sense that it is concerned with semiotic reality: that is, reality in the form of meaning. This dimension of reality is itself constructed by [the] other two metafunctions: the ideational, which construes a natural reality, and the interpersonal, which enacts an intersubjective reality. … The function of the textual metafunction is thus an enabling one with respect to the rest; it takes over the semiotic resources brought into being by the other two metafunctions and as it were operationalises them …
 In SFL theory, context is construed in semiotic terms: as a connotative semiotic system with language as its expression plane. On the other hand, Martin (1992: 33, 39-40, 121, 122) instead uses the term 'context' to refer to the (semiotic) co-text and the material setting.
 External conjunctive relations are a resource of the textual metafunction. The textual metafunction at the level of context is the system of MODE, whereas FIELD is the ideational dimension of context.
 In SFL theory, institutions are situation types. That is, theoretically they are located halfway down the cline of instantiation at the level of context. Thus they differ by probabilities in the context systems of FIELD, TENOR and MODE — not just field.
 Genre, in the sense of the different rôles that language plays, is a system of MODE at the level of context — not a stratum of context.
Genre, in the sense of text type, is a point on the cline of instantiation. It is register viewed from the instance pole of the cline.
In SFL theory, therefore, genres are registers that vary according to different feature probabilities in the system of MODE — that is, in terms of the textual metafunction.