tailieunhanh - Báo cáo khoa học: "Automatically Evaluating Text Coherence Using Discourse Relations"

We present a novel model to represent and assess the discourse coherence of text. Our model assumes that coherent text implicitly favors certain types of discourse relation transitions. We implement this model and apply it towards the text ordering ranking task, which aims to discern an original text from a permuted ordering of its sentences. | Automatically Evaluating Text Coherence Using Discourse Relations Ziheng Lin Hwee Tou Ng and Min-Yen Kan Department of Computer Science National University of Singapore 13 Computing Drive Singapore 117417 linzihen nght kanmy @ Abstract We present a novel model to represent and assess the discourse coherence of text. Our model assumes that coherent text implicitly favors certain types of discourse relation transitions. We implement this model and apply it towards the text ordering ranking task which aims to discern an original text from a permuted ordering of its sentences. The experimental results demonstrate that our model is able to significantly outperform the state-of-the-art coherence model by Barzilay and Lap-ata 2005 reducing the error rate of the previous approach by an average of 29 over three data sets against human upper bounds. We further show that our model is synergistic with the previous approach demonstrating an error reduction of 73 when the features from both models are combined for the task. 1 Introduction The coherence of a text is usually reflected by its discourse structure and relations. In Rhetorical Structure Theory RST Mann and Thompson 1988 observed that certain RST relations tend to favor one of two possible canonical orderings. Some relations . Concessive and Conditional favor arranging their satellite span before the nucleus span. In contrast other relations . Elaboration and Evidence usually order their nucleus before the satellite. If a text that uses non-canonical relation orderings is rewritten to use canonical orderings it often improves text quality and coherence. This notion of preferential ordering of discourse relations is observed in natural language in general 997 and generalizes to other discourse frameworks aside from RST. The following example shows a Contrast relation between the two sentences. 1 Everyone agrees that most of the nation s old bridges need to be repaired or replaced. S1 But there s .