• First, existing studies of utterance modeling mainly focus on representing utterances by using bidirectional GRU<cite> (Xing et al., 2017)</cite> or unidirectional GRU (Tian et al., 2017 ). One is the attention-based approach<cite> (Xing et al., 2017)</cite> , the other is the sequential integration approach (Tian et al., 2017) . • Utterance Representations: Bidirectional GRU vs. Unidirectional GRU<cite> Xing et al. (2017)</cite> utilized a bidirectional GRU and a word-level attention mechanism to transfer word representations to utterance representations. • Inter-utterance Representations: Attention vs. Sequential Integration<cite> Xing et al. (2017)</cite> proposed a hierarchical attention mechanism to feed the utterance representations to a backward RNN to obtain contextual representation.