Halliday & Matthiessen (1999: 551-2):
(5) Complementaritytransitivity (i): transitive perspectivedry = 'make dry' (cf. wipe)transitivity (ii): ergative perspectivedry = 'become dry' (cf. fade)
As discussed in Chapter 4 above, the grammar adopts two complementary perspectives on agency, the transitive and the ergative. Most processes are oriented primarily within one perspective or the other; here we have illustrated the complementarity with a verb that is at home in both.