摘要： Chapter8 Analyzing Sentence Structure 分析句子结构 Earlier chapters focused on words: how to identify them, analyze their structure, assign them to lexical categories, and access their meanings. We have also seen how to identify patterns in word sequences or n-grams. However, these methods only scratch .. 阅读全文

摘要： 7.8Further Reading Extra materials for this chapter are posted at http://www.nltk.org/, including links to freely available resources on the web. For more examples of chunking with NLTK, please see the Chunking HOWTO at http://www.nltk.org/howto. The popularity of chunking is due in great part to .. 阅读全文

摘要： 7.9Exercises 练习 ☼ The IOB format categorizes tagged tokens as I, O and B. Why are three tags necessary? What problem would be caused if we used I and O tags exclusively? ☼ Write a tag pattern to match noun phrases containing plural head nouns, e.g. "many/JJ researchers/NNS",... 阅读全文

摘要： 7.7Summary 小结 Information extraction systems search large bodies of unrestricted text for specific types of entities and relations, and use them to populate well-organized databases. These databases can then be used to find answers for specific questions. The typical architecture... 阅读全文