Bidirectional Directed Acyclic Graph Neural Network for Aspect-level Sentiment Classification

To achieve outstanding aspect-level sentiment analysis (ASC), it is crucial to reduce the distance between aspect terms and opinion words. Recently, advanced methods in ASC used graph neural network (GNN)-based methods to leverage the syntactic dependency within the sentence, which can shorten the distance through syntactical dependencies. However, existing approaches that utilize GNNs have difficulty extracting long-distance relations in the dependency tree due to the over-smoothing problem resulting from stacking GNN layers, which limits their ability to detect remote relations. To solve this issue, we propose a Bidirectional Directed Acyclic Graph (BDAG) to reconstruct syntactic dependencies and a Bidirectional Directed Acyclic Graph Neural Network (BDAGNN) to efficiently propagate multi-hop sentiment information. We also enhance the BDAG with affective commonsense knowledge from SenticNet for comprehensive sentiment classification. The BDAGNN we proposed obtains partial state-of-the-art performance on four benchmark datasets, indicating the feasibility of encoding syntactic structures with BDAG.