关键词: 汉语词法分析，字标注，上下文，分词，词性标注，命名实体识别

Abstract: Chinese lexical analysis is a foundational task for Chinese information processing. At the current, the main- stream technology of Chinese lexical analysis is based on statistical methods. These methods treat the analysis process as a sectuence data tagging problem. Context is the necessary resource not only for obtaining linguistic knowledge in sta- tistical linguistics but also for solving the problem in natural language processing. Chinese lexical analysis needs the help of correlative context. However, are above and below the same important? To overcome the lack of giving the result by the subjective experience,we studied the contribution of above and below for character-based tagging Chinese lexical a- nalysis via the large number of experiments about word segmentation, PUS tagging and named entity recognition. Closed evaluations were performed on many kinds of corpus from the international Chinese language processing 13akeoff, and comparative experiments were performed on different feature templates which describe above-context and below-con- text. Experimental results show that the performance by the below-context increases 6 percentage points than by the a- bovccontcxt.

Key words: Chinese lexical analysis, Character tagging, Context, Word segmentation, POS tagging, Named entity recogtion