expanded by the very instantiations that realise it and that is continuously reproduced and recreated with use. Another way to understand the difference in concerns between systemic functional grammar and most variants of generative grammar is through Chomsky's claim that "linguistics is a sub-branch of psychology". Halliday investigates linguistics more as a sub-branch of sociology. SFG therefore pays much more attention to pragmatics and discourse semantics than is traditionally the case in formalism. The orientation of systemic functional grammar has served to encourage several further grammatical accounts that deal with some perceived weaknesses of the theory and similarly orient to issues not seen to be addressed in more structural accounts. Examples include the model of Richard Hudson called word grammar, and William B. McGregor's Semiotic Grammar which revises the organization of the metafunctions. See also Systemic linguistics Thematic equative Other significant systemic functional grammarians: Ruqaiya Hasan J.R. Martin C.M.I.M. Matthiessen Linguists also involved with the early development of the approach: Randolph Quirk Richard Hudson References External links For more information, see the SFG web site at: Systemic functional grammar For a large bibliography containing the vast majority of systemic functional writings, see the bibliography site at: Word grammar Layman's introduction: A simple description of using SFG techniques in language and literacy tuition . Grammar frameworks