Incorporating multi-level CNN and attention mechanism for Chinese clinical named entity recognition

Named entity recognition (NER) is a fundamental task in Chinese natural language processing (NLP) tasks. Recently, Chinese clinical NER has also attracted continuous research attention because it is an essential preparation for clinical data mining. The prevailing deep learning method for Chinese clinical NER is based on long short-term memory (LSTM) network. However, the recurrent structure of LSTM makes it difficult to utilize GPU parallelism which to some extent lowers the efficiency of models. Besides, when the sentence is long, LSTM can hardly capture global context information. To address these issues, we propose a novel and efficient model completely based on convolutional neural network (CNN) which can fully utilize GPU parallelism to improve model efficiency. Moreover, we construct multi-level CNN to capture short-term and long-term context information. We also design a simple attention mechanism to obtain global context information which is conductive to improving model performance in sequence labeling tasks. Besides, a data augmentation method is proposed to expand the data volume and try to explore more semantic information. Extensive experiments show that our model achieves competitive performance with higher efficiency compared with other remarkable clinical NER models.