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This paper describes a novel approach towards the empirical approximation of discourse relations between different utterances in texts. Following the idea that every pair of events comes with preferences regarding the range and frequency of discourse relations connecting both parts, the paper investigates whether these preferences are manifested in the distribution of relation words (that serve to signal these relations). | Towards the Unsupervised Acquisition of Discourse Relations Christian Chiarcos Information Sciences Institute University of Southern California 4676 Admiralty Way Marina del Rey CA 90292 chiarcos@daad-alumni.de Abstract This paper describes a novel approach towards the empirical approximation of discourse relations between different utterances in texts. Following the idea that every pair of events comes with preferences regarding the range and frequency of discourse relations connecting both parts the paper investigates whether these preferences are manifested in the distribution of relation words that serve to signal these relations . Experiments on two large-scale English web corpora show that significant correlations between pairs of adjacent events and relation words exist that they are reproducible on different data sets and for three relation words that their distribution corresponds to theorybased assumptions. 1 Motivation Texts are not merely accumulations of isolated utterances but the arrangement of utterances conveys meaning human text understanding can thus be described as a process to recover the global structure of texts and the relations linking its different parts Vallduvi 1992 Gernsbacher et al. 2004 . To capture these aspects of meaning in NLP it is necessary to develop operationalizable theories and within a supervised approach large amounts of annotated training data. To facilitate manual annotation weakly supervised or unsupervised techniques can be applied as preprocessing step for semimanual annotation and this is part of the motivation of the approach described here. 213 Discourse relations involve different aspects of meaning. This may include factual knowledge about the connected discourse segments a subjectmatter relation e.g. if one utterance represents the cause for another Mann and Thompson 1988 p.257 argumentative purposes a presentational relation e.g. one utterance motivates the reader to accept a claim formulated in another .
