Halliday & Matthiessen (1999: 467-8):
In the participant-organising perspective, it is the nature of the participants involved in the process that determines the different process types. Relevant variables include the following:1. Is some participant created, brought into existence, by the process?2. Is some participant restricted to conscious being?3. Can some participant be a metathing as well as a thing?4. Is the process directed towards some participant?5. Does the process benefit some participant?6. Does the process occur spontaneously or does it need an input of energy?7. Does the process affect some participant materially or does it impinge on its consciousness?8. Is the process symmetric?9. Is the process reflexive?Questions such as these lead to typologies with terms like action, transaction, happening, sensing, saying, relation, existential, ambient, and so on. In the typology presented here as part of the ideation base, there are two very general considerations:1. process type: what kind of reality does the figure or process configuration pertain to (the material world, the world of consciousness, the world of symbolisation, the world of abstract relations)?2. agency: is the occurrence of the process (in conjunction with the medium) caused by an entity that is external to it (an agent)?