... Niu2, Ming Zhou2, Ting Liu1, Sheng Li11Harbin Institute of Technology, Harbin, China{zhaosq,tliu,lisheng}@ir.hit.edu.cn2Microsoft Research Asia, Beijing, China{chengniu,mingzhou}@microsoft.comAbstractThis ... allowed to keep unchanged in para-phrasing. This is a difference between paraphras-ing and MT, since all words should be translated in MT. In our experiments, all the words that occur in the ... fragments occurring in identical contexts as paraphrases from one bil-lion web documents. Since web mining is rathertime consuming, we do not exploit the web to ex-tract paraphrases in this paper.So...