Although recent studies on multi-task learning framework suggest that closely related tasks can improve each other mutually from separated supervision information (Ma et al., 2018;Cerisara et al., 2018;, the acquisition of sentence (or utterance)-level sentiment labels, which is required by multi-task learning, remains a laborious and expensive endeavor.
coarse-grained document (or dialogue)-level annotations are relatively easy to obtain due to the widespread use of opinion grading interfaces (e.g., ratings).