CMSC723 LING645 FINAL REVIEW 12 08 04 1 Part of Speech Tagging What is the difference between open and closed word classes What is the relation between these classes and word frequency in arbitrary documents POS Ambiguity How do we tell the difference between that and that in I consider that odd 2 Rule Based Tagger Provide some rules to correctly tag a word with an appropriate POS given its context Compare this process of POS tagging to context free parsing What do they have in common How do they differ 3 Stochastic Tagger Why should the HMM approach do better than choosing the most frequent tag 4 Consider the following data a Secretariat NNP is VBZ expected VBN to TO race VB tomorrow NN b People NNS continue VBP to TO inquire VB the DT reason NN for IN the DT race NN for IN outer JJ space NN Suppose we know this from the Brown Corpus P NN TO 021 P NN IN 03 P VB TO 34 P VB IN 002 P race NN 00041 P race VB 00003 Find the most probable POS for a word if the preceding tag is known For example suppose we know the POS of the word preceding race What is the most likely POS for race in each of these cases and explain your answers i to TO race ii the DT race Now what if the preceding tag is not known 5 Transformation Based Tagger TBL Combination of Rule based and stochastic tagging methodologies a b c d e What does it require How does it work What does it learn How is it iterative What does this system return 6 Problem Given a particular tagged corpus that I present give the highest frequency POS for the word race Show the corpus re tagged according to highest frequency tags Give two example rules that might be learned by a TBL technique to change incorrectly tagged words in re tagged corpus to their correct tags 7 Context Free Grammars and Parsing Subcategorization frames eat 0 prefer NP show NP NP give NP PPto fly PPfrom PPto What happens when there is movement How does this complicate the CFG Example Where do you want to fly to 8 How do we represent the auxiliary system in CFG modal perfect progressive passive 9 Earley How does one retrieve a parse tree from an Earley parse 10 Provide a first order predicate logic representation for each of the following sentences a All of John s friends own a car b Some of John s friends don t own a car c A friend or relative of John lends John a car 11 Provide the truth table for P Q R for all Boolean values of P Q and R 12 Lexical Semantics a How is polysemy different from synonymy b What semantic relations are used in Wordnet Give an example of each relation 13 What is the principle of compositionality Why is it relevant 14 What is the difference between precision and recall Under what circumstances might one be more important than the other 15 What are the advantages of using a parser for entity extraction and what are the problems 16 What is a question target and what are ways to determine it
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