6、自然语言理解的技术方法与工具选择

自然语言理解的技术方法与工具选择

一、基于规则的方法

1.1 词性标注（POS tagging）

词性标注并非简单地在字典中查找单词并标注词性，因为许多单词有多种词性。例如，在句子 “We would like to book a flight from Boston to London” 中，“book” 在此处作动词，但它也常作名词。词性标注算法不仅要考虑单词本身，还要结合上下文来确定正确的词性。在这个例子中，“book” 跟在 “to” 后面，“to” 常表明下一个词是动词。以下是该句子的词性标注表：
| Word | Part of speech | Meaning of part of speech label |
| — | — | — |
| we | PRP | Personal pronoun |
| would | MD | Modal verb |
| like | VB | Verb, base form |
| to | TO | To (this word has its own part of speech) |
| book | VB | Verb, base form |
| a | DT | Determiner (article) |
| flight | NN | Singular noun |
| from | IN | Preposition |
| Boston | NNP | Proper noun |
| to | TO | To |
| London | NNP | Proper noun |