To overcome the data sparseness problem, deepneural-network-based methods have attracted much attention because of their ability to use dense feature representations (Socher et al., 2011;Socher et al., 2013;Kim, 2014;Kalchbrenner et al., 2014;Tai et al., 2015;Zhang and Komachi, 2015).
tree-structured approaches called recursive neural networks (RvNNs) have been shown to perform well in sentiment classification tasks (Socher et al., 2011;Socher et al., 2013;Kim, 2014;Tai et al., 2015).