Halliday & Matthiessen (2004: 482):
Parallel to projected information (propositions) is the projection of goods-&-services (proposals), which similarly may be paratactic, hypotactic, or embedded as Qualifier to a noun; and again the phenomenon may be verbal (locution, projected by the processes offer, command, suggest/suggestion, etc) or mental (idea, projected by intend/intention wish, hope, etc). The difference in the mental processes is that propositions are projected by cognitive processes whereas proposals are projected by desiderative ones.