Rhetoric And Intentions In Discourse

On the face of it these theories are rather similar: both provide hierarchical characterisations of texts, and both seem concerned with the purpose of the text for GSDT, the text realizes the intentional structure that underlies it; and for R.ST, the text is structured in terms of the rhetorical relations that hold between its parts. But these similarities are only skin deep. The kinds of trees used by the two theories are actually quite different: in GSDT, text can appear at both leaf nodes and internal nodes in the trees; whereas in RST, text can only appear at leaf nodes. So the structures might be isomorphic trader some mapping but that mapping remains to be worked out (at the very least, isonaorphism could only be achiew~d by annotating arcs iu an intentional structure tree with "rhetorical" labels; there is an interesting parallel here with the dilference between dependency grammar and phrase structure gramnaar). A more significant, difference is that, in RST, leaf nodes (the atomic text spans) are typically taken to be single clauses; but in GSDT, if our atomic elements (the bottom level discourse segments) were clauses, then, given the constraints the theory claims on pronominalization and reference, we'd rule out as anomolous a large space of perfectly legitimate pronominalizations (those where the antecedent and anaphor are in clauses at the same level of embedding in the discourse structure: recall that material in a sister discourse segment is inaccessible). Given this, it would be hard to argue that RST's text spans correspond to GSDT's discourse segments.