Paraphrasing of Chinese Utterances

Paraphrasing of Chinese Utterances Yujie Zhang∗ Communications Research Laboratory 2-2-2, Hikaridai, Seika-cho, Soraku-gun, Kyoto 619-0289 Japan yujie@crl.go.jp Kazuhide Yamamoto ATR Spoken Language Translation Research Laboratories 2-2-2, Hikaridai, Seika-cho, Soraku-gun, Kyoto 619-0288 Japan yamamoto@fw.ipsj.or.jp Abstract One of the key issues in spoken language trans- lation is how to deal with unrestricted expres- sions in spontaneous utterances. This research is centered on the development of a Chinese paraphraser that automatically paraphrases ut- terances prior to transfer in Chinese-Japanese spoken language translation. In this paper, a pattern-based approach to paraphrasing is pro- posed for which only morphological analysis is required. In addition, a pattern construction method is described through which paraphras- ing patterns can be efficiently learned from a paraphrase corpus and human experience. Us- ing the implemented paraphraser and the ob- tained patterns, a paraphrasing experiment was conducted and the results were evaluated. 1 Introduction In spoken language translation one of the key issues is how to deal with unrestricted expres- sions in spontaneous utterances. To resolve this problem, we have proposed a paraphrasing ap- proach in which the utterances are automati- cally paraphrased prior to transfer (Yamamoto et al., 2001; Yamamoto, 2002). The paraphras- ing process aims to bridge the gap between the unrestricted expressions in the input and the limited expressions that the transfer can trans- late. In fact, paraphrasing actions are often seen in daily communication. When a listener can- not understand what a speaker said, the speaker usually says it again using other words, i.e., he paraphrases. In a Chinese-Japanese spoken lan- guage translation system, the pre-processing of Chinese utterances is involved and we attempt to apply a paraphrasing approach. This paper ∗ This work was done when the author stayed at ATR Spoken Language Translation Research Laboratories. is focused on the paraphrasing of Chinese utter- ances. Some cases of paraphrasing research with cer- tain targets have been reported. For example, there has been work on rewriting the source language in machine translation with a focus on reducing syntactic ambiguities (Shirai et al., 1993), research on paraphrasing paper titles with a focus on transforming syntactic struc- tures to achieve readability (Sato, 1999), and research on paraphrasing Japanese in summa- rization with a focus on transforming a noun modifier into a noun phrase (Kataoka et al., 1999). We have reported some research on Chinese paraphrasing (Zhang and Yamamoto, 2001; Zhang et al., 2001; Zong et al., 2001). The techniques of paraphrasing natural language can be applied not only to the pre-processing of machine translation but also to information retrieval and summarization. 2 Goals and Approach In the pre-processing stage of translation, Chi- nese paraphrasing focuses on (1) transforming the expressions of spoken lan- guage into formal expressions, (2) reducing syntactic and semantic ambigui- ties, (3) generating as many different expressions as possible in order to include expressions that can be translated by the transfer, and (4) paraphrasing the main constituents of the utterance in case the paraphrasing of the whole utterance has no effect. The aim of paraphrasing types …

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