Halliday & Matthiessen (1999: 178, 179):
Being elements, participants and processes occupy roles in figures; but whereas processes only serve in the single role of Process, participants (as we have seen) range over a much wider experiential spectrum — the direct participant roles of Actor, Goal, Senser, Phenomenon, and so on, and also the indirect participant roles within circumstances such as Location and Cause. Thus, seen from the point of view of figures, participants are construed as being experientially more complex, in the sense that they can take on a variety of configurational roles: see Figure 5-1. This difference between participants and processes is also reflected in differences in their internal organisations, as we shall suggest below
