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← Unit 22 01 Sentence Structuremp4

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Showing Revision 2 created 05/24/2016 by Udacity Robot.

  1. So far everything we've said about language has to deal with the probability distribution over words.
  2. So we take a sentence, "Fed raises interest rates," and we compute a probability for that,
  3. and we do that in terms of the probability of some words given neighboring words.
  4. But there's another approach to language processing that deals not just with adjacency of words, but with an underlying tree structure that's hidden,
  5. that's not apparent in the sequence of words, but which represents the underlying structure, and perhaps meaning of the sentence.
  6. So we can say that "Fed" is a noun, and by itself it's a noun phrases, "raises" is a verb, "interest" is a noun,
  7. and "rates" is also a noun. And together they make up a noun phrase. And now we have a verb with its object makes up a verb phrase.
  8. And then a noun phrase as a subject, and a verb phrase as the main part of the sentence, makes up a sentence.
  9. And that's our tree that represents a part of this sentence.
  10. Now, however, one of the factors that's important here is that this tree is not unique. This seems to make a lot of sense.
  11. This says that "the Fed" is a subject of this sentence, and the object is "the interest rates," and they're being raised.
  12. But we can think of other parses that also makes sense to some degree for this sentence.
  13. For example, "interest" is also a verb, and it could be that "rates" is a noun which is serving as a noun phrase.
  14. And so the verb phrase could be "interest rates." What is doing that interest of rates?
  15. Well, it could be "Fed raises." A certain type of raises called Fed raises, they interest something, and what they're interesting is the rates.
  16. And that could be a sentence. And that sentence seems less likely, but they're both valid parses of this sentence.