Halliday & Matthiessen (2014: 659-60):
Through the accumulation of logogenetic patterns and through the resources of cohesion, lexicogrammar makes a considerable contribution to the development of patterns in a text that extend beyond a single grammatical unit such as the clause, or even a complex of units such as the clause complex; and this is, of course, why lexicogrammatical analysis of a text can tell us so much about how it works. The patterns that are developed in this way are, however, patterns of meaning, not patterns of wording; they are patterns at the level of semantics rather than at the level of lexicogrammar. This is so because text is, as we have emphasised, a semantic phenomenon in the first instance; it is meaning unfolding in some particular context of situation. For example, the grammatical system of conjunction gives speakers and writers the resources to mark transitions in the development of a text – i.e., to mark rhetorical relations used to expand the text step by step; and the rhetorical relations that are marked in this way by conjunctions are semantic relations organising the text as a flow of meaning.
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A logogenetic pattern is a pattern of instantiation; that is, a pattern of feature selection and realisation statement activation. Different patterns identify different texts, and different patterns of patterns identify difference 'above' the instance pole of the cline of instantiation. A logogenetic pattern thus includes selections from the lexicogrammatical system of cohesion.