Sentence segmentation and named entity recognition are two significant tasks in ancient Chinese processing since punctuation and named entity information are important for further research on ancient classics. These two are sequence labeling tasks in essence so we can tag the labels of these two tasks for each token simultaneously. Our work is to evaluate whether such a unified way would be better than tagging the label of each task separately with a BERT-based model. The paper adopts a BERT-based model that was pre-trained on ancient Chinese text to conduct experiments on Zuozhuan text. The results show there is no difference between these two tagging approaches without concerning the type of entities and punctuation. The ablation experiments show that the punctuation token in the text is useful for NER tasks, and finer tagging sets such as differentiating the tokens that locate at the end of an entity and those are in the middle of an entity could offer a useful feature for NER while impact negatively sentences segmentation with unified tagging.

The basic tasks of ancient Chinese information processing include automatic sentence segmentation, word segmentation, part-of-speech tagging and named entity recognition. Tasks such as lexical analysis need to be based on sentence segmentation because of the reason that a plenty of ancient books are not punctuated. However, step-by-step processing is prone to cause multi-level diffusion of errors. This paper designs and implements an integrated annotation system of sentence segmentation and lexical analysis. The BiLSTM-CRF neural network model is used to verify the generalization ability and the effect of sentence segmentation and lexical analysis on different label levels on four cross-age test sets. Research shows that the integration method adopted in ancient Chinese improves the F1-score of sentence segmentation, word segmentation and part of speech tagging. Based on the experimental results of each test set, the F1-score of sentence segmentation reached 78.95, with an average increase of 3.5%; the F1-score of word segmentation reached 85.73%, with an average increase of 0.18%; and the F1-score of part-of-speech tagging reached 72.65, with an average increase of 0.35%.