Named Entity Recognition by Using XLNet-BiLSTM-CRF

Named entity recognition (NER) is the basis for many natural language processing (NLP) tasks such as information extraction and question answering. The accuracy of the NER directly affects the results of downstream tasks. Most of the relevant methods are implemented using neural networks, however, the word vectors obtained from a small data set cannot describe unusual, previously-unseen entities accurately and the results are not sufficiently accurate. Recently, the use of XLNet as a new pre-trained model has yielded satisfactory results in many NLP tasks, integration of XLNet embeddings in existent NLP tasks is not straightforward. In this paper, a new neural network model is proposed to improve the effectiveness of the NER by using a pre-trained XLNet, bi-directional long-short term memory (Bi-LSTM) and conditional random field (CRF). Pre-trained XLNet model is used to extract sentence features, then the classic NER neural network model is combined with the obtained features. In addition, the superiority of XLNet in NER tasks is demonstrated. We evaluate our model on the CoNLL-2003 English dataset and WNUT-2017 and show that the XLNet-BiLSTM-CRF obtains state-of-the-art results.