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DiscourseandSummarization
Prof.SameerSinghCS295:STATISTICALNLP
WINTER2017
March16,2017
BasedonslidesfromDanJurafsky,JacobEisenstein,andeveryoneelsetheycopiedfrom.
Upcoming…
• Finalreportdueinaweek:March20,2017• Instructionsup:ACLstyle,5pages(+references)Project
2CS295:STATISTICALNLP(WINTER2017)
Outline
Discourse
3
Summarization
Wrapup
CS295:STATISTICALNLP(WINTER2017)
Outline
Discourse
4
Summarization
Wrapup
CS295:STATISTICALNLP(WINTER2017)
Discourse
5
Coreference
Coherence
Relations
Resolvingentities andevents.
Whatmakesthetextcoherent?
Rhetorical andnarrative linksbetweenunits
CS295:STATISTICALNLP(WINTER2017)
Discourse
6
Coreference
Coherence
Relations
Resolvingentities andevents.
Whatmakesthetextcoherent?
Rhetorical andnarrative linksbetweenunits
CS295:STATISTICALNLP(WINTER2017)
Coherence
7CS295:STATISTICALNLP(WINTER2017)
Coherence
8CS295:STATISTICALNLP(WINTER2017)
CoherencevsSemantics
9
Ameaninglesssentencecanbegrammatical..
Colorlessgreenideassleepfuriously
Thediscourseequivalentofgrammaticalityiscoherence
Canacoherenttextbewithoutmeaning?
CS295:STATISTICALNLP(WINTER2017)
ExampleEssay
10CS295:STATISTICALNLP(WINTER2017)
ExampleEssay
11
Thesecondreasonforthefive-paragraphthemeisthatitmakesyoufocusonasingletopic.Somepeoplestartwritingontheusualtopic,likeTVcommercials,andtheywindupallovertheplace,talkingaboutwhereTVcamefromorcapitalismorhealthfoodsorwhatever.Butwithonlyfiveparagraphsandonetopicyou’renottemptedtogetbeyondyouroriginalidea,likecommercialsareagoodsourceofinformationaboutproducts.Yougiveyourthreeexamples,andzap!you’redone.Thisisanotherwaythefive-paragraphthemekeepsyoufromthinkingtoomuch.
CS295:STATISTICALNLP(WINTER2017)
Detecting“Coherency”
12CS295:STATISTICALNLP(WINTER2017)
DiscourseConnectors
13CS295:STATISTICALNLP(WINTER2017)
LexicalChains
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DiscourseRelations
15
1.Intoday’ssociety,collegeisambiguous.2.Weneedittolive,3.butwealsoneedittolove.4.Moreover,withoutcollegemostoftheworld’slearningwouldbeegregious.5.College,however,hasmyriadcosts.6.Oneofthemostimportantissuesfacingtheworldishowtoreducecollegecosts.7.Somehavearguedthatcollegecostsareduetotheluxuriesstudentsnowexpect.8.Othershavearguedthatthecostsarearesultofathletics.9.Inreality,highcollegecostsaretheresultofexcessivepayforteachingassistants
CS295:STATISTICALNLP(WINTER2017)
DiscourseRelations
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1.Intoday’ssociety,collegeisambiguous.2.Weneedittolive,3.butwealsoneedittolove.4.Moreover,withoutcollegemostoftheworld’slearningwouldbeegregious.5.College,however,hasmyriadcosts.6.Oneofthemostimportantissuesfacingtheworldishowtoreducecollegecosts.7.Somehavearguedthatcollegecostsareduetotheluxuriesstudentsnowexpect.8.Othershavearguedthatthecostsarearesultofathletics.9.Inreality,highcollegecostsaretheresultofexcessivepayforteachingassistants
CS295:STATISTICALNLP(WINTER2017)
DiscourseRelations
17
1.Intoday’ssociety,collegeisambiguous.2.Weneedittolive,3.butwealsoneedittolove.4.Moreover,withoutcollegemostoftheworld’slearningwouldbeegregious.5.College,however,hasmyriadcosts.6.Oneofthemostimportantissuesfacingtheworldishowtoreducecollegecosts.7.Somehavearguedthatcollegecostsareduetotheluxuriesstudentsnowexpect.8.Othershavearguedthatthecostsarearesultofathletics.9.Inreality,highcollegecostsaretheresultofexcessivepayforteachingassistants
CS295:STATISTICALNLP(WINTER2017)
DiscourseRelations
18
1.Intoday’ssociety,collegeisambiguous.2.Weneedittolive,3.butwealsoneedittolove.4.Moreover,withoutcollegemostoftheworld’slearningwouldbeegregious.5.College,however,hasmyriadcosts.6.Oneofthemostimportantissuesfacingtheworldishowtoreducecollegecosts.7.Somehavearguedthatcollegecostsareduetotheluxuriesstudentsnowexpect.8.Othershavearguedthatthecostsarearesultofathletics.9.Inreality,highcollegecostsaretheresultofexcessivepayforteachingassistants
CS295:STATISTICALNLP(WINTER2017)
DiscourseRelations
19
1.Intoday’ssociety,collegeisambiguous.2.Weneedittolive,3.butwealsoneedittolove.4.Moreover,withoutcollegemostoftheworld’slearningwouldbeegregious.5.College,however,hasmyriadcosts.6.Oneofthemostimportantissuesfacingtheworldishowtoreducecollegecosts.7.Somehavearguedthatcollegecostsareduetotheluxuriesstudentsnowexpect.8.Othershavearguedthatthecostsarearesultofathletics.9.Inreality,highcollegecostsaretheresultofexcessivepayforteachingassistants
CS295:STATISTICALNLP(WINTER2017)
DiscourseRelations
20
1.Intoday’ssociety,collegeisambiguous.2.Weneedittolive,3.butwealsoneedittolove.4.Moreover,withoutcollegemostoftheworld’slearningwouldbeegregious.5.College,however,hasmyriadcosts.6.Oneofthemostimportantissuesfacingtheworldishowtoreducecollegecosts.7.Somehavearguedthatcollegecostsareduetotheluxuriesstudentsnowexpect.8.Othershavearguedthatthecostsarearesultofathletics.9.Inreality,highcollegecostsaretheresultofexcessivepayforteachingassistants
CS295:STATISTICALNLP(WINTER2017)
CoherenceStructure
21
Segmentation
Zoning/Ordering
Centering/Salience
1.Intoday’ssociety,collegeisambiguous.2.Weneedittolive,3.butwealsoneedittolove.4.Moreover,withoutcollegemostoftheworld’slearningwouldbeegregious.5.College,however,hasmyriadcosts.6.Oneofthemostimportantissuesfacingtheworldishowtoreducecollegecosts.7.Somehavearguedthatcollegecostsareduetotheluxuriesstudentsnowexpect.8.Othershavearguedthatthecostsarearesultofathletics.9.Inreality,highcollegecostsaretheresultofexcessivepayforteachingassistants
CS295:STATISTICALNLP(WINTER2017)
CoherenceStructure
22
Segmentation`
Zoning/Ordering
Centering/Salience
1.Intoday’ssociety,collegeisambiguous.2.Weneedittolive,3.butwealsoneedittolove.4.Moreover,withoutcollegemostoftheworld’slearningwouldbeegregious.5.College,however,hasmyriadcosts.6.Oneofthemostimportantissuesfacingtheworldishowtoreducecollegecosts.7.Somehavearguedthatcollegecostsareduetotheluxuriesstudentsnowexpect.8.Othershavearguedthatthecostsarearesultofathletics.9.Inreality,highcollegecostsaretheresultofexcessivepayforteachingassistants
CS295:STATISTICALNLP(WINTER2017)
CoherenceStructure
23
Segmentation
Zoning/Ordering
Centering/Salience
1.Intoday’ssociety,collegeisambiguous.2.Weneedittolive,3.butwealsoneedittolove.4.Moreover,withoutcollegemostoftheworld’slearningwouldbeegregious.5.College,however,hasmyriadcosts.6.Oneofthemostimportantissuesfacingtheworldishowtoreducecollegecosts.7.Somehavearguedthatcollegecostsareduetotheluxuriesstudentsnowexpect.8.Othershavearguedthatthecostsarearesultofathletics.9.Inreality,highcollegecostsaretheresultofexcessivepayforteachingassistants
1.Intoday’ssociety,collegeisambiguous.2.Weneedittolive,3.butwealsoneedittolove.4.Moreover,withoutcollegemostoftheworld’slearningwouldbeegregious.5.College,however,hasmyriadcosts.6.Oneofthemostimportantissuesfacingtheworldishowtoreducecollegecosts.7.Somehavearguedthatcollegecostsareduetotheluxuriesstudentsnowexpect.8.Othershavearguedthatthecostsarearesultofathletics.9.Inreality,highcollegecostsaretheresultofexcessivepayforteachingassistants
CS295:STATISTICALNLP(WINTER2017)
CoherenceStructure
24
Segmentation
Zoning/Ordering
Centering/Salience
1.Intoday’ssociety,collegeisambiguous.2.Weneedittolive,3.butwealsoneedittolove.4.Moreover,withoutcollegemostoftheworld’slearningwouldbeegregious.5.College,however,hasmyriadcosts.6.Oneofthemostimportantissuesfacingtheworldishowtoreducecollegecosts.7.Somehavearguedthatcollegecostsareduetotheluxuriesstudentsnowexpect.8.Othershavearguedthatthecostsarearesultofathletics.9.Inreality,highcollegecostsaretheresultofexcessivepayforteachingassistants
1.Intoday’ssociety,collegeisambiguous.2.Weneedittolive,3.butwealsoneedittolove.4.Moreover,withoutcollegemostoftheworld’slearningwouldbeegregious.5.College,however,hasmyriadcosts.6.Oneofthemostimportantissuesfacingtheworldishowtoreducecollegecosts.7.Somehavearguedthatcollegecostsareduetotheluxuriesstudentsnowexpect.8.Othershavearguedthatthecostsarearesultofathletics.9.Inreality,highcollegecostsaretheresultofexcessivepayforteachingassistants
1.Intoday’ssociety,collegeisambiguous.2.Weneedittolive,3.butwealsoneedittolove.4.Moreover,withoutcollegemostoftheworld’slearningwouldbeegregious.5.College,however,hasmyriadcosts.6.Oneofthemostimportantissuesfacingtheworldishowtoreducecollegecosts.7.Somehavearguedthatcollegecostsareduetotheluxuriesstudentsnowexpect.8.Othershavearguedthatthecostsarearesultofathletics.9.Inreality,highcollegecostsaretheresultofexcessivepayforteachingassistants
CS295:STATISTICALNLP(WINTER2017)
ApplicationsofCoherence
25
SentenceOrdering
Whengeneratingsummaries,reordertillsentencesarecoherent.
ReadabilityAssessment Isapieceoftexteasilyreadable?
CS295:STATISTICALNLP(WINTER2017)
Discourse
26
Coreference
Coherence
Relations
Resolvingentities andevents.
Whatmakesthetextcoherent?
Rhetorical andnarrative linksbetweenunits
CS295:STATISTICALNLP(WINTER2017)
DiscourseRelations
27CS295:STATISTICALNLP(WINTER2017)
UseinSentimentAnalysis
28CS295:STATISTICALNLP(WINTER2017)
Outline
Discourse
29
Summarization
Wrapup
CS295:STATISTICALNLP(WINTER2017)
TextSummarizationGoal:produceanabridgedversionofatextthatcontainsinformationthatisimportantorrelevanttoauser.
SummarizationApplications◦ outlinesorabstractsofanydocument,article,etc◦ summariesofemailthreads◦ actionitemsfromameeting◦ simplifyingtextbycompressingsentences
30CS295:STATISTICALNLP(WINTER2017)
Whattosummarize?Single-documentsummarization◦ Givenasingledocument,produce◦ abstract◦ outline◦ headline
Multiple-documentsummarization◦ Givenagroupofdocuments,producea“gist”:◦ aseriesofnewsstoriesonthesameevent◦ asetofwebpagesaboutsometopicorquestion
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Query-focusedvsGenericGenericsummarization:◦ Summarizethecontentofadocument
Query-focusedsummarization:◦ summarizeadocumentwithrespecttoaninformationneedexpressedinauserquery.
◦ akindofcomplexquestionanswering:◦ Answeraquestionbysummarizingadocumentthathastheinformationtoconstructtheanswer
32CS295:STATISTICALNLP(WINTER2017)
Extractivesummarization&AbstractivesummarizationExtractivesummarization:◦ createthesummaryfromphrasesorsentencesinthesourcedocument(s)
Abstractivesummarization:◦ expresstheideasinthesourcedocumentsusing(atleastinpart)differentwords
33CS295:STATISTICALNLP(WINTER2017)
Summarization:ThreeStages1. contentselection:choosesentencestoextractfromthedocument
2. informationordering:chooseanordertoplacetheminthesummary
3. sentencerealization:cleanupthesentences
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DocumentSentence
SegmentationSentenceExtraction
All sentencesfrom documents
Extracted sentences
Information Ordering
Sentence Realization
Summary
Content Selection
Sentence Simplification
CS295:STATISTICALNLP(WINTER2017)
Simplifyingsentences
appositives Rajam,28,anartistwhowaslivingatthetimeinPhiladelphia,foundtheinspirationinthebackofcitymagazines.
attribution clauses Rebelsagreedtotalkswithgovernmentofficials,internationalobserverssaidTuesday.
PPswithoutnamed entities
ThecommercialfishingrestrictionsinWashingtonwillnotbeliftedunlessthesalmonpopulationincreases[PPtoasustainablenumber]]
initialadverbials “Forexample”,“Ontheotherhand”,“Asamatteroffact”,“Atthispoint”
CS295:STATISTICALNLP(WINTER2017) 35Zajic etal.(2007),Conroyetal.(2006),Vanderwende etal.(2007)
Simplestmethod:parsesentences,userulestodecidewhichmodifierstoprune(morerecentlyawidevarietyofmachine-learningmethods)
ROUGE(RecallOrientedUnderstudyforGistingEvaluation)Intrinsicmetricforautomaticallyevaluatingsummaries◦ BasedonBLEU(ametricusedformachinetranslation)◦ Notasgoodashumanevaluation(“Didthisanswertheuser’squestion?”)◦ Butmuchmoreconvenient
GivenadocumentD,andanautomaticsummaryX:◦ HaveNhumansproduceasetofreferencesummariesofD◦ Runsystem,givingautomaticsummaryX◦ WhatpercentageofthebigramsfromthereferencesummariesappearinX?
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ROUGE − 2 =min(count(i,X),count(i,S))
bigrams i∈S∑
s∈{RefSummaries}∑
count(i,S)bigrams i∈S∑
s∈{RefSummaries}∑
CS295:STATISTICALNLP(WINTER2017)
Outline
Discourse
37
Summarization
Wrapup
CS295:STATISTICALNLP(WINTER2017)
WordoutofContext
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WordsinContext
39CS295:STATISTICALNLP(WINTER2017)
Sentences
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InformationExtraction
CS295:STATISTICALNLP(WINTER2017) 41
MachineTranslation
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Other“Applications”
43CS295:STATISTICALNLP(WINTER2017)
DocumentDocumentDocument
DocumentDocume
ntDocumentDocume
ntDocument
Question Processing
PassageRetrieval
Query Formulation
Answer Type Detection
Question
Passage Retrieval
Document Retrieval
Answer Processing
Answer
passages
Indexing
RelevantDocs
DocumentDocumentDocument
DocumentSentence
SegmentationSentenceExtraction
All sentencesfrom documents
Extracted sentences
Information Ordering
Sentence Realization
Summary
Content Selection
Sentence Simplification
Wrapup oftheCourse
CS295:STATISTICALNLP(WINTER2017) 44
AndNow!
CS295:STATISTICALNLP(WINTER2017) 45
DoresearchinNLP!
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