Integrate Syntax Information for Target-Oriented Opinion Words Extraction with Target-Specific Graph Convolutional Network.

Target-oriented Opinion Words Extraction (TOWE) aims to identify opinion words toward a specific target given the sentence. Syntax structure, which contains dependency relationships among words, is a vital clue for this task. With the help of syntax structure as a constraint, the model could remove irrelevant words and focus on tokens that are relevant to the given target. Directly adapting existing syntactic-based methods faces the problem that these models do not explicitly learn target-centric representations. Another challenge is that prior works only learn fixed order dependency relations, while context words require syntactic information in different scales. To handle these issues, we propose Target-Specific Graph Convolutional Network (TS-GCN) to explicitly integrate dependency structure. The proposed method could build high-quality syntax-aware representations by propagating target information to syntactically related words via graph convolution. Furthermore, we design a memory-based module to dynamically learn multi-granularity syntactic knowledge and infuse local features. Experimental results demonstrate the effectiveness of our method, and we achieve state-of-the-art performances on four SemEval datasets.