Difference between revisions of "Gildea and Jurafsky Computational Linguistics 2002"

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(Created page with '== Citation == Daniel Gildea and Daniel Jurafsky. 2002. Automatic Labeling of Semantic Roles. Computational Linguistics, 28(3):245-288. == Online version == [http://delivery.a…')
 
 
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== Online version ==
 
== Online version ==
  
[http://delivery.acm.org/10.1145/1150000/1141330/p235-zhou.pdf?key1=1141330&key2=0111885821&coll=GUIDE&dl=&CFID=106800160&CFTOKEN=10813007 ACM portal]
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[http://www.mitpressjournals.org/doi/pdf/10.1162/089120102760275983 MIT Press]
  
 
== Summary ==
 
== Summary ==
  
The [[Category::paper]] presents a MEDical Information Extraction (MedIE) system, which extracts patient information from free-text clinical records.  
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The [[Category::paper]] presents a system for [[AddressesProblem::Semantic Role Labeling]], whose roles are defined at the level of semantic frames of the type. For instance, the JUDGEMENT frame contains roles like JUDGE, EVALUEE, and REASON, amd tje STATEMENT frame contains roles like SPEAKER, ADDRESSEE, and MESSAGE.
  
They divided their extraction job into three tasks below.
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(1) [She''/Judge''] '''blames''' [the Government''/Evaluee''][for failing to do enough to help''/Reason''].
* Extraction of medical terms
 
* [[AddressesProblem::Relation Extraction]
 
**In this paper, relation extraction means extraction of associated medical concepts. For example, 'Blood pressure' and '144/90' are associated terms in the sentence, "Blood pressure is 144/90".
 
* [[AddressesProblem::Text Classification]]
 
**For example, a patient can be classified as a former smoker, a current smoker, or a non-smoker
 
  
Their approaches are:
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(2) ["I'll knock on your door at quarter to six"''/Message''][Susan''/Speaker''] '''said'''.
* An ontology-based approach for extracting medical terms of interest
 
**They used Unified Medical Language System (UMLS). About terms that are not defined in UMLS, they predicted categories of some terms using sentence structures.
 
* A graph-based approach which uses the parsing result of link-grammar parser for [[AddressesProblem::Relation Extraction]]
 
**Notable things in their approach are three. First, they included the processing of negation. Second, when the parser fails, they used a pattern-based approach. Lastly, they replaced multi-word terms with placeholders because the parser did not process the terms.  
 
* an NLP-based feature extraction method coupled with an ID3-based [[AddressesProblem::Decision Tree Learning]] for [[AddressesProblem::Text Classification]]
 
  
  
This approach was fairly successful mostly showing over 80% of precision and recall. However, the system was tested on the data written by only a clinician, which means that the style of free-text records was consistent. Nevertheless, the research is worth in that they applied various IE techniques to the free-text clinical records, explain about the problems they encountered.
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They define semantic roles at the frame level. They use the [[UsesDataset::FrameNet]] database including nouns and adjectives as well as verbs. However, they also did experiments on more general semantic role (thematic role) labeling.
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Their job is mainly divided into two tasks: finding the frame boundaries and assigning the semantic role to the frames.
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Features used for probability estimation for roles include phrase type, governing category, parse tree path, position, voice, and head word. They built a classifier by combining probabilities from distributions conditioned on a variety of subsets of the features because they will have seen the combination of all features only a small number of times, providing a poor estimate of the probability. To combine the strengths of the various distributions, they used various ways to obtain an estimate of the full distribution, such as [[UsesMethod::linear interpolation]][http://en.wikipedia.org/wiki/Linear_interpolation], EM linear interpolation, geometric mean [http://en.wikipedia.org/wiki/Geometric_mean], backoff lineanr interpolation, and backoff geometric mean.
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To generalize lexical statistics, they compared three different approaches: automatic clustering, use of a hand-built ontological resource, WordNet, and boostrapping. Automatic clustering and WordNet hierarchy were used only for noun phrases.
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The system gives 82% accuracy in identifying the semantic role of pre-segmented constituents, 65% precision and 61% recall in both segmenting constituents and identifying their semantic role.  
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== Key Contribution ==
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This system is the first statistical model on FrameNet solving the semantic role labeling problem, and future systems use the features introduced in this paper as a baseline. This paper is also very worth to read in that it describes the whole process of semantic role labeling in detail. In addition, they did many various experiments to find out which features, algorithms, and techniques affect the performance of the system.
  
 
== Related papers ==
 
== Related papers ==
 
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An interesting follow-up paper is [[RelatedPaper::Palmer et al Computational Linguistics 2005]] which applies the features and the probability model here to the PropBank dataset.
An interesting follow-up paper is [[RelatedPaper::Denecke and Bernauer AIME 2007]] which uses semantic structures to extract medical information.
 

Latest revision as of 22:21, 30 November 2010

Citation

Daniel Gildea and Daniel Jurafsky. 2002. Automatic Labeling of Semantic Roles. Computational Linguistics, 28(3):245-288.

Online version

MIT Press

Summary

The paper presents a system for Semantic Role Labeling, whose roles are defined at the level of semantic frames of the type. For instance, the JUDGEMENT frame contains roles like JUDGE, EVALUEE, and REASON, amd tje STATEMENT frame contains roles like SPEAKER, ADDRESSEE, and MESSAGE.

(1) [She/Judge] blames [the Government/Evaluee][for failing to do enough to help/Reason].

(2) ["I'll knock on your door at quarter to six"/Message][Susan/Speaker] said.


They define semantic roles at the frame level. They use the FrameNet database including nouns and adjectives as well as verbs. However, they also did experiments on more general semantic role (thematic role) labeling.


Their job is mainly divided into two tasks: finding the frame boundaries and assigning the semantic role to the frames.


Features used for probability estimation for roles include phrase type, governing category, parse tree path, position, voice, and head word. They built a classifier by combining probabilities from distributions conditioned on a variety of subsets of the features because they will have seen the combination of all features only a small number of times, providing a poor estimate of the probability. To combine the strengths of the various distributions, they used various ways to obtain an estimate of the full distribution, such as linear interpolation[1], EM linear interpolation, geometric mean [2], backoff lineanr interpolation, and backoff geometric mean.


To generalize lexical statistics, they compared three different approaches: automatic clustering, use of a hand-built ontological resource, WordNet, and boostrapping. Automatic clustering and WordNet hierarchy were used only for noun phrases.


The system gives 82% accuracy in identifying the semantic role of pre-segmented constituents, 65% precision and 61% recall in both segmenting constituents and identifying their semantic role.

Key Contribution

This system is the first statistical model on FrameNet solving the semantic role labeling problem, and future systems use the features introduced in this paper as a baseline. This paper is also very worth to read in that it describes the whole process of semantic role labeling in detail. In addition, they did many various experiments to find out which features, algorithms, and techniques affect the performance of the system.

Related papers

An interesting follow-up paper is Palmer et al Computational Linguistics 2005 which applies the features and the probability model here to the PropBank dataset.