“…The two-step methods (Elsner and Charniak, 2008, 2010, 2011Chen et al, 2017;Jiang et al, 2018;Kummerfeld et al, 2019) firstly retrieve the relations between two messages, e.g., "reply-to" relations (Guo et al, 2018;, and then adopt a clustering algorithm to construct individual sessions. The end-to-end models (Tan et al, 2019;Yu and Joty, 2020), instead, perform the disentanglement operation in an end-to-end manner, where the context information of detached sessions will be exploited to classify a message to a session. End-to-end models tend to achieve better performance than two-step models, but both often need large annotated data to get fully trained , which is expensive to obtain and thus encourages the demand on unsupervised algorithms.…”