Thus various types of rhetorical or coherence relations (between clauses or larger discourse segments) have been proposed in the literature, e.g., by Hobbs (1979), Grosz &amp; Sidner (1986), and Mann &amp; Thompson (1988). Proposed coherence relations are ones like elaboration, exemplification, parallelism, and contrast. We defer further discussion of rhetorical structure to section 6 (on language generation).