Deletion-based Korean Sentence Compression using Graph Neural Networks

Gyoung-Ho Lee, Yo-Han Park, Kong Joo Lee

http://doi.org/10.5626/JOK.2022.49.1.32

Automatic sentence compression aims at generating a concise sentence from a lengthy source sentence. Most common approaches to sentence compression is deletion-based compression. In this paper, we implement deletion-based sentence compression systems based on a binary classifier and long short-term memory (LSTM) networks with attention layers. The binary classifier, which is a baseline model, classifies words in a sentence into words that need to be deleted and words that will remain in a compressed sentence. We also introduce a graph neural network (GNN) in order to employ dependency tree structures when compressing a sentence. A dependency tree is encoded by a graph convolutional network (GCN), one of the most common GNNs, and every node in the encoded tree is input into the sentence compression module. As a conventional GCN deals with only undirected graphs, we propose a directed graph convolutional network (D-GCN) to differentiate between parent and child nodes of a dependency tree in sentence compression. Experimental results show that the baseline model is improved in terms of the sentence compression accuracy when employing a GNN. Regarding the performance comparison of graph networks, a D-GCN achieves higher F1 scores than a GCN when applied to sentence compression. Through experiments, it is confirmed that better performance can be achieved for sentence compression when the dependency syntax tree structure is explicitly reflected.