For a sentence s containing such a collocation c, since the in-sentence features are always ambiguous, it is difficult to disambiguate the polarity of c by using them.
meanwhile, it also brings us lots of interesting and challenging research topics, such as subjectivity analysis (Riloff and Wiebe, 2003), sentiment classification (Pang et al., 2002;Kim and Hovy, 2005;Wilson et al., 2009;He et al., 2011), opinion retrieval (Zhang et al., 2007;Zhang and Ye, 2008;Li et al., 2010) and so on.