Traditionally, grammar has always been a grammar of written language: and it has always been a product grammar ['Product' is here used as one term of the Hjelmslevian pair process/product.] A process/product distinction is a relevant one for linguists because it corresponds to that between our experience of speech and our experience of writing: writing exists whereas speech happens.
Halliday (1985, p. xxiii) cited in: David Brazil (1995) A Grammar of Speech. p. 10.