Martin (1992: 494):
Halliday (1978: 122) outlines the semiotic structure of context as follows:
The semiotic structure of the situation is formed out of the three sociosemiotic variables of field, tenor and mode. These represent in systematic form the type of activity in which the text has significant function (field), the status and rôle relationships involved (tenor) and the symbolic mode and rhetorical channels that are adopted.
Halliday's intrinsic theory of language function is thus projected onto context as an extrinsic theory of language use. The realisation relationship between context and language is treated as a symbolic one, with language a metaphor for social reality at the same time as social reality is a metaphor for language. … Seen from the perspective of culture on the other hand, context can be alternatively interpreted as a system of social processes.
 This continues the misunderstanding of realisation and, within this, the misinterpretation of symbolic as metaphorical, and, within this, the misunderstanding of metaphor. In SFL theory, context and language are modelled as levels of symbolic abstraction, such that language realises context. If the notion of metaphor is applied to the relation between context and language, then the claim would be that context may be realised congruently or metaphorically in language. To claim that the higher level of abstraction, context, is a metaphor for the lower, language, misunderstands metaphor in precisely the same way as saying semantics is a metaphor for lexicogrammar. On the contrary, semantics may be realised in lexicogrammar either congruently or metaphorically.
 This confuses different orders of experience: semiotic and material. In SFL theory, context is construed as a semiotic system; the Halliday quote above makes this clear in its opening words: 'the semiotic structure of the situation'. Social processes, on the other hand, are of the material order of experience. Despite interpreting context materially as social reality, it will be seen that Martin's model of context is concerned with the semiotic order: genre and register.