These supervised methods obtain high accuracies on newswire (Xue and Shen, 2003;Zhang and Clark, 2007;Jiang et al., 2009;Zhao et al., 2010;Sun and Xu, 2011).
manually annotated training data mostly come from the news domain, and the performance can drop severely when the test data shift from newswire to blogs, computer forums, and Internet literature (Liu and Zhang, 2012;).Supervised approaches often have a high requirement on the quality and quantity of annotated corpus, which is always not easy to build.