Halliday & Matthiessen (1999: 428-9):
Within systemic-functional linguistics, Fawcett (e.g. 1980) has pioneered a "cognitive model of an interactive mind". There are many fundamental similarities with the approach we are taking here, e.g. in construing an experiential system of process configuration within the content plane. However, there are two related differences of particular interest in the context of our present discussion:
(i) in Fawcett's model, there is only one system-structure cycle within the content plane: systems are interpreted as the semantics, linked through a "realisation component" to [content] form, which includes items and syntax, the latter being modelled structurally but not systemically;(ii) in Fawcett's model, the semantics is separate from the "knowledge of the universe", with the latter as a "component" outside the linguistic system including "long term memory" and "short term sort of knowledge".
Blogger Comments:
This is misleading, because 'form' in Fawcett's model also includes expression. Fawcett (2010: 35n, 39):
I take a different view, as this book shows, in that I regard the level of meanings within the 'lexicogrammar' as the key level of linguistically-realised meaning, such that it is realised in any one of (1) syntax, (2) intonation or punctuation (depending on the medium of discourse) and (3) items. …
The term "form" is used here in a wider sense than that in "Categories" (or indeed any of Halliday's later writings) because it includes, as well as syntax and grammatical and lexical items, components for intonation or punctuation (depending on whether the medium is speech or writing).