Halliday & Matthiessen (2014: 593-4):
How can we model text as an ongoing process of meaning? To do this, we return to the concept of the cline of instantiation… . The system of a language is instantiated as text, the two representing the poles at either end of the cline of instantiation. System and text are not different phenomena; they are simply complementary phases of one and the same phenomenon. When seen up close, this phenomenon appears to us as text; but when we adopt a more distant observer perspective, we can build up a picture of it as system. System and text form a cline rather than a dichotomy, because between these two poles there is a semiotic region of intermediate patterns (conceived of as instance types – as text types, or as subsystems – as registers).
Text is thus the process of instantiation; and we can characterise it by reference to the system as the selection of systemic options unfolding through time.
Blogger Comment:
Note that SFL Theory models 'register' as a subsystem of language, not a system of context, and 'genre', in the sense of 'text type', as an instance type of language, not a system of context.