Halliday & Matthiessen (1999: 152-3, 152n):
The 'doing' figure is based prototypically on a schema we might refer to as "action and impact". There is always an Actor, the participant that performs the Process; and in an example such as the boys were jumping, the Process stops there — that is all there is to it. But in examples such as the boys were throwing stones, or the stones hit the wall the Actor's performance of the Process extends beyond, so as to 'impact' on another participant — this is the one known as the Goal (see Figure 4-8).
In the typical case (the "active voice", in grammatical terminology), the clause unfolds iconically, reflecting the movement of the impact from Actor to Goal.⁶ And, as we saw above, the latter may then be followed by representation of the outcome of the impact — a resultative Attribute (he knocked it flat), a circumstance of Role (he cut it into cubes), or a circumstance of Location (he threw it into the corner).⁶ This iconicity is, however, easily overridden by the textual metafunction, which has its own mode of iconic realisation.