Segmenting a chunk of text into words is usually the first step of processing Chinese text, but its necessity has rarely been explored. In this paper, we ask the fundamental question of whether Chinese word segmentation (CWS) is necessary for deep learning-based Chinese Natural Language Processing. We benchmark neural word-based models which rely on word segmentation against neural char-based models which do not involve word segmentation in four end-to-end NLP benchmark tasks: language modeling, machine translation, sentence matching paraphrase and text classification. Through direct comparisons between these two types of models, we find that char-based models consistently outperform word-based models. Based on these observations, we conduct comprehensive experiments to study why word-based models underperform char-based models in these deep learning-based NLP tasks. We show that it is because word-based models are more vulnerable to data sparsity and the presence of out-of-vocabulary (OOV) words, and thus more prone to overfitting. We hope this paper could encourage researchers in the community to rethink the necessity of word segmentation in deep learning-based Chinese Natural Language Processing. Yuxian Meng and Xiaoya Li contributed equally to this paper.
@cite_8: This paper presents the results from the ACL-SIGHAN-sponsored First International Chinese Word Segmentation Bakeoff held in 2003 and reported in conjunction with the Second SIGHAN Workshop on Chinese Language Processing, Sapporo, Japan. We give the motivation for having an international segmentation contest (given that there have been two within-China contests to date) and we report on the results of this first international contest, analyze these results, and make some recommendations for the future.
Since the First International Chinese Word Segmentation Bakeoff in 2003 @cite_8 , a lot of effort has been made on Chinese word segmentation.