Halliday & Matthiessen (2014: 43):
If the situation is one of ‘meaning’ in terms of the sociosemiotic activity then the entire structure of the situation is projected onto the text. For example, in a situation of telling a traditional folk tale, the structure would be (from Hasan, 1984, but slightly simplified):
(Placement ^ ) Initiating Event ^ Sequent Event¹⁻ⁿ ^ Final Event ( ^ Finale) (° Moral)
This structure is projected onto the text operating in the situation – and possibly also onto other accompanying semiotic processes such as a musical score. Each element, or stage, of the structure of the situation is realised by distinctive semantic patterns, as illustrated for Placement by Hasan (1984). These distinctive semantic patterns are, in turn, realised by distinctive lexicogrammatical patterns; but the patterns of wording in the lexicogrammar are always mediated by the patterns of meaning in the semantics.
This new addition to IFG by Halliday's reviser, Matthiessen, reinterprets Hasan's work on 'Generic Structure Potential' (GSP) as 'context structure projected onto text structure'.
Hasan (1984) was concerned with deriving semantic structure 'from above', that is: from context, in accordance with the trinocular perspective advocated by Halliday, together with the principle that a functional theory prioritises the view 'from above'.
Hasan was concerned with semantic structure potential of particular genres, or text types; that is, of particular registers.
Here Matthiessen reinterprets Hasan's register-specific semantic structure potential as the structure of an instance of context that is projected onto the semantic structure of an instance of language.
Note that the aspects of the situation that are not projected onto the structure of the text include:
- what's going on (field), e.g. a parent reading to a child at bed-time;
- who's involved, e.g. the tenor relation between parent and child; and
- the rôle of language, e.g. spoken mode.