This paper outlines a number of problems with RST's elaboration relation, and discusses a new model of text structure that results from leaving this relation out of the set of relations. In this model, trees of interclausal/intersentential relations account for the local coherence of a text, while its global coherence is accounted for by a separate device: global focus. 1 Introduction Many theories of discourse propose that a coherent text is one whose clauses, sentences and text spans (or perhaps the propositions expressed by these text units) stand in particular relations to one another. The basic motivation in these theories stems from the observation that a text is more than a sequence of independent units: whether a particular unit makes sense in a given discourse depends not only on this unit by itself, but also on its relationship with the other units in the discourse. This claim has been spelled out in many dierent ways, but there are two requirements that any such theor...

In this paper, we propose a generalization of Centering Theory (CT) (Grosz, Joshi, Weinstein (1995)) called Veins Theory (VT), which extends the applicability of centering rules from local to global discourse. A key facet of the theory involves the identification of "veins" over discourse structure trees such as those defined in RST, which delimit domains of referential accessibility for each unit in a discourse. Once identified, reference chains can be extended across segment boundaries, thus enabling the application of CT over the entire discourse. We describe the processes by which veins are defined over discourse structure trees and how CT can be applied to global discourse by using these chains. We also define a discourse "smoothness" index which can be used to compare different discourse structures and interpretations, and show how VT can be used to abstract a span of text in the context of the whole discourse. Finally, we validate our theory by analyzing examples from corpora of English, French, and Romanian.

This paper investigates whether the model of local rhetorical coherence suggested in Knott et al. (2001) can boost the performance of the Centering-based metrics of entity coherence employed by Karamanis et al. (2004) for the task of information ordering. Rhetorical coherence is integrated into the way Centering’s basic data structures are derived from the annotated features of the GNOME corpus. The results indicate that (a) the simplest metric continues to perform better than its competitors even when local rhetorical coherence is taken into account, and (b) this extra coherence constraint decreases its performance. Keywords: Information Ordering, Centering Theory, Rhetorical Coherence. 1.

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Algorithms for discourse processing commonly assume that texts are tree-structured,

Many text documents in the legal domain are created in order to express the reasoning steps a decision maker followed in reaching conclusions. For example, refugee law determinations are documents that express the reasoning steps a member of the Refugee Review Tribunal in Australia followed in order to infer conclusions regarding the status of an applicant. Although, it is reasonable to expect that a mapping between the reasoning steps used by a decision maker and the structure of the document produced would clearly be apparent, a number of authors have discovered that such a mapping is by no means obvious. In order to develop legal knowledge based systems that generate documents from their own reasoning steps, discourse analysis is invoked to bridge the gap and perform the mapping. In this paper, we articulate a heuristic that we use to generate a plausible document structure without the use of discourse analysis. Without discourse analysis, the heuristic cannot contribute to our unde...