Halliday & Matthiessen (1999: 123):
Many text types are heavily influenced by patterns in the meaning base — they can be seen as ‘macro-figures’, i.e. as expansions of figures by means of logico-semantic relations. This is not to say that that the relationship between organisation in the meaning base and the discoursal organisation is always one-to-one even when a text is organised according to an ideational sequence. In particular, a text may leave to be inferred certain steps that would be specified in the sequence in the meaning base (e.g. to make explicit the inferential processes involved).