Also in the spirit of lessening confusion (pace Chris), JRM’s 1992 argument for positioning genre ‘above’, configuring selections in field, mode and tenor, is long and very heteroglossic, but this little para presents one angle...Overall it would appear that "rhetorical purpose" is the wild card in contextual description, being variously categorised under field (Halliday 1965), tenor (Gregory 1967), mode (Halliday 1978a, 1985/1989) and as a separate contextual variable in its own right (Firth 1950 — effects, Ure & Ellis 1977 — role, Fawcett 1980 — pragmatic purpose). The main reason for this is that purpose is difficult to associate with any one metafunctional component of the lexicogrammar or discourse semantics. The effect of a text is the result of all components of its meaning. This makes associating the notion of rhetorical purpose with Bakhtin's more global notion of speech genres an attractive one (cf. Gregory 1982).H&H … apply the term register from the perspective of language, looking ‘up’ at field, mode and tenor. JRM applies it from the perspective of field, mode and tenor, looking ‘down’ at language (and other modalities). Hence register and genre theory.
The linguistic features which are typically associated with a configuration of situational features — with particular values of the field, mode and tenor — constitute a register.
Martin, on the other hand, simply misapplies the term 'register' to the situational features instead of the linguistic features.
[5] The word 'hence' is misleading, because it gives the false impression that the validity of 'register and genre theory' has been supported by the text that precedes it.