29rhet_reI (ELABORATION,3,[1,2]) rhet_rel (ELABORATION,[4,6], 3) Once the elementary units of a text have been determined and the rhetorical relations between them have been hypothesized at sentence, paragraph, and section levels, we need to determine the rhetorical structures that are consistent with these hypotheses and with the constraints specific to valid RS-trees.
we need to solve the problem of rhetorical structure derivation.