Martin (1992: 405):
The notion of context will be developed in somewhat different directions in Chapter 7 below, where context of situation and context of culture will be construed as a series of connotative semiotics (named register, genre and ideology).
 This is one of the most far-reaching misunderstandings of SFL theory in the entire book. In SFL theory, 'context' is a semiotic system that is realised in language; it is the culture conceived as a connotative semiotic. The terms 'register' and 'genre', on the other hand, refer to functional varieties of language itself; registers and genres are not more abstract than language — they are language.
The distinction between register and context is clearly stated in the work most cited by Martin. Halliday & Hasan (1976: 22):
The linguistic features which are typically associated with a configuration of situational features — with particular values of field, mode and tenor — constitute a REGISTER. The more specifically we can characterise the context of situation, the more specifically we can predict the properties of a text in that situation.
 The relation between context of situation and context of culture is instantiation, whereas relations between stratified semiotic systems is realisation. Turning the theory back on itself, instantiation is an intensive attributive relation, whereas realisation is an intensive identifying relation. This means it is fundamentally flawed to construe context of situation and context of culture (instantiation) 'as a series of connotative semiotics' (realisation) — even before relabelling them as types of language (register and genre).