Halliday & Matthiessen (1999: 192):
object (semiotic)typifying role: scope-defining participant in figure of saying [Range in verbal process, e.g. read the notice, tell me a story]; also active participant [Sayer, e.g. the book says.,., the regulations require... ].pronoun it/them, they; general noun (none); number category: count (singular/plural).may also exist as material object, e.g. book, clock; has potential for being symbol source [hence Sayer in projecting clause].