Halliday & Matthiessen (2004: 587):
A text does not ‘consist of’ clauses (clause complexes) — there is no part–whole or ‘constituency’ relationship between a text and a clause (complex) and there is no single rank scale with text and clause as ranks. Rather, a text is realised by clauses (clause complexes), the two being located on different strata — semantics (the stratum of meaning) and lexicogrammar (the stratum of wording), respectively.