Halliday & Matthiessen (1999: 318):
… we referred to projection as something that overlaps the ‘boundary’ between interpersonal and ideational metafunctional space; in English it is typically construed ideationally, though with a close relationship to the interpersonal systems of modality and mood. Other languages locate projection rather differently in relation to this boundary, sometimes foregrounding its interpersonal aspects, for example through a special category of ‘reporting’ mood.