Towards Selective Data Enhanced Implicit Discourse Relation Recognition via Reinforcement Learning

As a fundamental task in NLP, recognizing implicit discourse relations remains a challenging problem for years. One of the most important reasons is the limited amounts of annotated data. On one hand, most existing methods use multi-task methods to enlarge data. External datasets are often fully introduced to the training process which may lead to a negative transfer of noisy data. On the other hand, some previous researches on selecting data mostly focus on designing rules with heuristic methods. It should be difficult to cover all aspects of good samples. Another drawback is that data selection can hardly generally fit well in any other recognition model since it was specialized with a specific discourse relation classifier.In this paper, we propose a novel selective data enhanced model (SDE) based on reinforcement learning. Our model is a general framework, composed of two parts: 1) Discourse relation classifier is designed to identify relations, including multi-level representation module and relation recognition module. 2) Pseudo labeled data selector is designed to pick out data that can enhance the discourse relation classifier. We conduct joint learning alternately to optimize both of the classifier and the selector. Our model is able to expand data selectively. And classifier part can be replaced with any other complicated networks. To further exploit interact signals between arguments, we also present a multi-level representation based on BERT. Experiments show that our model achieves better performance than state-of-the-art methods.