jurafsky&martin_3rdEd_17 (1).pdf

G gutenbergorg amazoncom imdbcom etc analyze your

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source (e.g., gutenberg.org, amazon.com, imdb.com, etc.). Analyze your list and give examples of ways that the names in it are likely to be problematic for the techniques described in this chapter. 21.4 Develop an NER system specific to the category of names that you collected in the last exercise. Evaluate your system on a collection of text likely to contain instances of these named entities. 21.5 Acronym expansion, the process of associating a phrase with an acronym, can be accomplished by a simple form of relational analysis. Develop a system based on the relation analysis approaches described in this chapter to populate a database of acronym expansions. If you focus on English Three Letter Acronyms (TLAs) you can evaluate your system’s performance by comparing it to Wikipedia’s TLA page. 21.6 A useful functionality in newer email and calendar applications is the ability to associate temporal expressions connected with events in email (doctor’s appointments, meeting planning, party invitations, etc.) with specific calendar entries. Collect a corpus of email containing temporal expressions related to event planning. How do these expressions compare to the kinds of expressions commonly found in news text that we’ve been discussing in this chapter? 21.7 Acquire the CMU seminar corpus and develop a template-filling system by using any of the techniques mentioned in Section 21.5 . Analyze how well your system performs as compared with state-of-the-art results on this corpus.
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CHAPTER 22 Semantic Role Labeling Understanding events and their participants is a key part of understanding natural language. At a high level, understanding an event means being able to answer the question “Who did what to whom” (and perhaps also “when and where”). The answers to this question may be expressed in many different ways in the sentence. For example, if we want to process sentences to help us answer question about a purchase of stock by XYZ Corporation, we need to understand this event despite many different surface forms. The event could be described by a verb ( sold, bought ) or a noun ( purchase ), and XYZ Corp can be the syntactic subject (of bought ) the indirect object (of sold ), or in a genitive or noun compound relation (with the noun purchase ), in the following sentences, despite having notationally the same role in all of them: XYZ corporation bought the stock. They sold the stock to XYZ corporation. The stock was bought by XYZ corporation. The purchase of the stock by XYZ corporation... The stock purchase by XYZ corporation... In this chapter we introduce a level of representation that lets us capture the commonality between these sentences. We will be able to represent the fact that there was a purchase event, that the participants in this event were XYZ Corp and some stock, and that XYZ Corp played a specific role, the role of acquiring the stock.
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