![](data:image/png;base64,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)
98 Chapter 3. 词法分析和语法分析基础 肖桐 朱靖波
3.4 句法分析
前面已经介绍了什么叫做“词”以及如何对分词问题进行统计建模。同时,也
介绍了如何对多个单词构成的命名实体进行识别。无论是分词还是命名实体识别都
是句子浅层信息的一种表示。对于一个自然语言句子来说,它更深层次的结构信息
可以通过更完整的句法结构来描述,而句法信息也是机器翻译和自然语言处理其他
任务中常用的知识之一。
3.4.1 句法树
句法(Syntax)是研究句子的每个组成部分和它们之间的组合方式。一般来说,
句法和语言是相关的,比如,英文是主谓宾结构,而日语是主宾谓结构,因此不同的
语言也会有不同的句法描述方式。自然语言处理领域最常用的两种句法分析形式是
短语结构句法分析(Phrase Structure Parsing)和依存句法分析(Dependency Parsing)。
图3.15展示了这两种的句法表示形式的实例。其中,左侧是短语结构树,它描述的是
短语的结构功能,比如“吃”是动词(记为 VV),“鱼”是名词(记为 NN),“吃/鱼”
组成动词短语,这个短语再与“喜欢”这一动词组成新的动词短语。短语结构树的
每个子树都是一个句法功能单元,比如,子树 VP(VV(吃) NN(鱼)) 就表示了“吃/鱼”
这个动词短语的结构,其中子树根节点 VP 是句法功能标记。短语结构树利用嵌套的
方式描述了语言学的功能,短语结构树中,每个词都有词性 (或词类),不同的词或者
短语可以组成名动结构、动宾结构等语言学短语结构,短语结构句法分析一般也被
称为成分句法分析(Constituency Parsing)或完全句法分析(Full Parsing)。
图3.15右侧展示的是另一种句法结构,被称作依存句法树。依存句法树表示了
句子中单词和单词之间的依存关系。比如,从这个例子可以了解,“猫”依赖“喜
欢”,“吃”依赖“喜欢”,“鱼”依赖“吃”。
IP 句子
VP 动
VP 动
NN名词
鱼
VV动词
吃
VV动词
喜欢
NP 名
NN名词
猫
猫
喜欢
吃
鱼
主谓
连动
谓宾
图 3.15 短语结构树 (左) 和依存树 (右)
短语结构树和依存句法树的结构和功能有很大不同。短语结构树的叶子节点是
单词,中间节点是词性或者短语句法标记。在短语结构句法分析中,通常把单词称
作终结符(Terminal),把词性称为预终结符(Pre-terminal),而把其他句法标记称为
非终结符(Non-terminal)。依存句法树没有预终结符和非终结符,所有的节点都是