There is a wide range of different logico-semantic relations any of which may hold between a primary and a secondary member of a clause complex. But it is possible to group these into a small number of general types, based on the two fundamental relationships of (1) EXPANSION and (2) PROJECTION [...] (2) Projection: the secondary clause is projected through the primary clause, which instates it as (a) a locution or (b) an idea.
- Halliday (1985), a pag.196