Paraphrases have been shown to be useful in plenty of areas, such as machine translation (MT) (Callison-Burch et al., 2006;Madnani et al., 2007;Marton et al., 2009), question answering (QA) (Lin and Pantel, 2001; Ravichandran and Hovy, 2002;Duboue and Chu-Carroll, 2006;Riezler et al., 2007), and web search (Zukerman and Raskutti, 2002).
the capability of paraphrasing is essential in web search, since in many cases the user queries need to be paraphrased so as to improve the quality of the search results.