CS388: Natural Language Processing Lecture 22: Queson ...gdurrett/courses/fa2019/... · Same en;ty...
Transcript of CS388: Natural Language Processing Lecture 22: Queson ...gdurrett/courses/fa2019/... · Same en;ty...
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CS388:NaturalLanguageProcessing
GregDurre8
Lecture22:Ques;on Answering2
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Recall:SQuAD
‣ Single-document,single-sentenceques;on-answeringtaskwheretheanswerisalwaysasubstringofthepassage
Rajpurkaretal.(2016)
‣ Predictstartandendindicesoftheanswerinthepassage
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Recall:Bidirec;onalA8en;onFlow
Seoetal.(2016)
Eachpassagewordnow“knowsabout”thequery
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Recall:QAwithBERT
Devlinetal.(2019)
WhatwasMarieCuriethefirstfemalerecipientof?[SEP]OneofthemostfamouspeopleborninWarsawwasMarie…
‣ Predictstartandendposi;onsofanswerinpassage‣ NoneedforcrazyBiDAF-stylelayers
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Recall:SQuADSOTA
‣ HarderQAsecngsareneeded
‣ Performanceisverysaturated
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ThisLecture
‣ Retrieval-basedQA/mul;-hopQA
‣ ProblemsinQA,especiallyrelatedtoanswertypeoverficng
‣ NewQAfron;ers
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ProblemsinQA
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AdversarialSQuAD‣ SQuADques;onsareoeeneasy:“whatwasshetherecipientof?”passage:“…recipientofNobelPrize…”
JiaandLiang(2017)
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AdversarialSQuAD
WhatwasMarieCuriethefirstfemalerecipientof?[SEP]…firstfemalerecipientoftheNobelPrize…
‣ BERTeasilylearnssurface-levelcorrespondenceslikethiswithself-a8en;on
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AdversarialSQuAD‣ SQuADques;onsareoeeneasy:“whatwasshetherecipientof?”passage:“…recipientofNobelPrize…”
JiaandLiang(2017)
‣ Canwemakethemharderbyaddingadistractoranswerinaverysimilarcontext?
‣ Takeques;on,modifyittolooklikeananswer(butit'snot),thenappendittothepassage
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AdversarialSQuAD
JiaandLiang(2017)
‣ Distractor“looks”moreliketheques;onthantherightanswerdoes,evenifen;;esarewrong
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WeaknesstoAdversaries
JiaandLiang(2017)
‣ Performanceofbasicallyeverymodeldropstobelow60%(whenthemodeldoesn'ttrainonthese)
‣ BERTvariantsalsoweaktothesekindsofadversaries
‣ Unlikeotheradversarialmodels,wedon’tneedtocustomizetheadversarytothemodel;thissinglesentencebreakseverySQuADmodel
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UniversalAdversarial“Triggers”
Wallaceetal.(2019)
‣ Adding“whyhowbecausetokillamericanpeople”causesSQuADmodelstoreturnthisanswer10-50%ofthe;mewhengivena“why"ques;on
‣ Similara8acksonotherques;ontypeslike“who”
‣ SimilartoJiaandLiang,butinsteadaddthesameadversarytoeverypassage
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HowtofixQA?‣ Be8ermodels?
‣ Be8erdatasets
‣ Butamodeltrainedonweakdatawilloeens;llbeweaktoadversaries‣ TrainingonJia+Liangadversariescanhelp,butthereareplentyofothersimilara8ackswhichthatdoesn'tsolve
‣ Sameques;onsbutwithmoredistractorsmaychallengeourmodels
‣ HarderQAtasks‣ Askques;onswhichcannotbeansweredinasimpleway
‣ Nextup:retrieval-basedQAmodels
‣ Aeerwards:mul=-hopQAandotherQAsecngs
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RetrievalModels
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Open-domainQA
‣ SQuAD-styleQAisveryar;ficial,notreallyarealapplica;on
‣ RealQAsystemsshouldbeabletohandlemorethanjustaparagraphofcontext—theore;callyshouldworkoverthewholeweb?
Q:WhatwasMarieCurietherecipientof?
MarieCuriewasawardedtheNobelPrizeinChemistryandtheNobelPrizeinPhysics…
MotherTeresareceivedtheNobelPeacePrizein…
CuriereceivedhisdoctorateinMarch1895…
Skłodowskareceivedaccoladesforherearlywork…
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Open-domainQA
‣ SQuAD-styleQAisveryar;ficial,notreallyarealapplica;on
‣ RealQAsystemsshouldbeabletohandlemorethanjustaparagraphofcontext—theore;callyshouldworkoverthewholeweb?
‣ QApipeline:givenaques;on:
‣ RetrievesomedocumentswithanIRsystem
‣ ZeroinontheanswerinthosedocumentswithaQAmodel
‣ Thisalsointroducesmorecomplexdistractors(badanswers)andshouldrequirestrongerQAsystems
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DrQA
Chenetal.(2017)
‣ Howoeendoestheretrievedcontextcontaintheanswer?(usesLucene)
‣ FullretrievalresultsusingaQAmodeltrainedonSQuAD:taskismuchharder
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RetrievalwithBERT
Leeetal.(2019)
‣ Canwedobe8erthanasimpleIRsystem?
‣ EncodethequerywithBERT,pre-encodeallparagraphswithBERT,queryisbasicallynearestneighbors
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Problems
Leeetal.(2019)
‣ManySQuADques;onsarenotsuitedtothe“open”secngbecausethey’reunderspecified
‣ SQuADques;onswerewri8enbypeoplelookingatthepassage—encouragesaques;onstructurewhichmimicsthepassageanddoesn’tlooklike“real”ques;ons
‣WheredidtheSuperBowltakeplace?
‣WhichplayerontheCarolinaPantherswasnamedMVP?
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NaturalQues;ons
Kwiatkowskietal.(2019)
‣ Ques;onsarosenaturally,unlikeSQuADques;onswhichwerewri8enbypeoplelookingatapassage.Thismakesthemmuchharder
‣ ShortanswerF1s<60,longanswerF1s
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Mul;-HopQues;onAnswering
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Mul;-HopQues;onAnswering
Welbletal.(2018),Yangetal.(2018)
‣ VeryfewSQuADques;onsrequireactuallycombiningmul;plepiecesofinforma;on—thisisanimportantcapabilityQAsystemsshouldhave
‣ Severaldatasetstestmul=-hopreasoning:abilitytoanswerques;onsthatdrawonseveralsentencesorseveraldocumentstoanswer
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WikiHop
FigurefromWelbletal.(2018)
‣ AnnotatorsshownWikipediaandaskedtoposeasimpleques;onlinkingtwoen;;esthatrequireathird(bridging)en;tytoassociate
‣ Amodelshouldn’tbeabletoanswerthesewithoutdoingsomereasoningabouttheintermediateen;ty
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HotpotQA
MeetCorlissArcherisanAmericantelevisionsitcomthatairedonCBS…
Ques%on:Whatgovernmentposi=onwasheldbythewomanwhoportrayedCorlissArcherinthefilmKissandTell?
ShirleyTempleBlackwasanAmericanactress,businesswoman,andsinger…
KissandTellisacomedyfilminwhich17-year-oldShirleyTempleactsasCorlissArcher.
…
…
Asanadult,sheservedasChiefofProtocoloftheUnitedStatesDoc1
Doc2
Sameen;ty
Doc3
Sameen;ty
ExamplepickedfromHotpotQA[Yangetal.,2018]
‣Muchlongerandmoreconvolutedques;ons
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Mul;-hopReasoning
TheOberoifamilyisanIndianfamilythatisfamousforitsinvolvementinhotels,namelythroughTheOberoiGroup
Ques%on:TheOberoifamilyispartofahotelcompanythathasaheadofficeinwhatcity?
TheOberoiGroupisahotelcompanywithitsheadofficeinDelhi.
…
…
Doc1
Doc2
Sameen;ty
Sameen;ty
ExamplepickedfromHotpotQA[Yangetal.,2018]
Thisisanidealizedversionofmul;-hopreasoning.Domodelsneedtodothistodowellonthistask?
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Mul;-hopReasoning
TheOberoifamilyisanIndianfamilythatisfamousforitsinvolvementinhotels,namelythroughTheOberoiGroup
Ques%on:TheOberoifamilyispartofahotelcompanythathasaheadofficeinwhatcity?
TheOberoiGroupisahotelcompanywithitsheadofficeinDelhi.
…
…
Doc1
Doc2
ExamplepickedfromHotpotQA(Yang2018)
Modelcanignorethebridgingen;tyanddirectlypredicttheanswer
Highlexicaloverlap
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Mul;-hopReasoning
MeetCorlissArcherisanAmericantelevisionsitcomthatairedonCBS…
Ques%on:Whatgovernmentposi=onwasheldbythewomanwhoportrayedCorlissArcherinthefilmKissandTell?
ShirleyTempleBlackwasanAmericanactress,businesswoman,andsinger…
KissandTellisacomedyfilminwhich17-year-oldShirleyTempleactsasCorlissArcher.
…
…
Asanadult,sheservedasChiefofProtocoloftheUnitedStatesDoc1
Doc2
Sameen;ty
Doc3
Sameen;ty
Nosimplelexicaloverlap.…butonlyonegovernmentposi;onappearsinthecontext!
ExamplepickedfromHotpotQA[Yangetal.,2018]
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Inves;ga;on
Canamodeliden;fytheanswerwithonlyasetofcandidates?
Canamodeliden;fywheretheanswerisinasinglehop?
Governmentposi=on ChiefofProtocol,actress,singer
OberoiFamily Delhi
ChenandDurre8(2019)
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FindingtheanswerdirectlyQues2on:Whatgovernmentposi;onwasheldbythewomanwhoportrayedCorlissArcherinthefilmKissandTell?
KaushikandLipton(2018)
ChiefofProtocolbusinesswoman…actress
MeetCorlissArcherisanAmericantelevisionsitcomthatairedonCBS…
ShirleyTempleBlackwasanAmericanactress,businesswoman,andsinger…
KissandTellisacomedyfilminwhich17-year-oldShirleyTempleactsasCorlissArcher.
Asanadult,sheservedasChiefofProtocoloftheUnitedStatesDoc1
Doc2
Doc3
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NoContextBaseline
DotProduct
Ques%on:Whatgovernmentposi=onwasheldbythewomanwhoportrayedCorlissArcherinthefilmKissandTell?
ChiefofProtocol businesswoman actress
Ques;onEncoder
AnswerEncoder
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ChiefofProtocol0.7
businesswoman0.2actress0.1
ChenandDurre8(2019)
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Accuracy
30
50
70
59.3
67.466.464.8
42.938.8
NoContextEn;ty-GCN
CFC BAGMajority-candidate
BiDAF
‣ SOTAmodelstrainedonthismaybelearningques;on-answercorrespondences,notmul;-hopreasoningasadver;sed
Morethanhalfofques;onscanbeansweredwithoutevenusingthecontext!
state-of-the-artweakbaselines
ResultsonWikiHop
NoContextEn;ty-GCN
CFC BAGMajority-candidate
BiDAF
ChenandDurre8(2019)
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Inves;ga;on
Canamodeliden;fytheanswerwithonlyasetofcandidates?
Canamodeliden;fywheretheanswerisinasinglehop?
Governmentposi=on ChiefofProtocol,actress,singer
OberoiFamily Delhi
ChenandDurre8(2019)
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SentenceFactoredModel
Findtheanswerbycomparingeachsentencewiththeques;onseparately!
Ques%on:TheOberoifamilyispartofahotelcompanythathasaheadofficeinwhatcity?
TheOberoiGroupisahotelcompanywithitsheadofficeinDelhi.
Doc2FutureFibreTechnologiesafibertechnologiescompany…
Doc3
TheOberoifamilyisanIndianfamilythatis…
Doc1
ChenandDurre8(2019)
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SentenceFactoredModel
TheOberoifamily…whatcity?
TheOberoiGroup…inDelhi.
FutureFibreTechnologiesisafibre…
TheOberoifamily…
Answerpredic;on:Delhi ‣Soemaxoverallsentencesistheonlycross-sentenceinterac;on
BiDAF BiDAFBiDAF
ChenandDurre8(2019)
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BiDAF++ QFE GRN DFGN SentenceFactored
F1
0
35
70
50.8
69.769.068.1
58.7
Asimplesinglesentencereasoningmodelcansolvemorethanhalfques;onsonHotpotQA.
ResultsonHotpotQA
BiDAF++ QFE GRN DFGN SentenceFactored
ChenandDurre8(2019)
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OtherWork
‣Minetal.ACL2019“Composi;onalQues;onsdonotNecessitateMul;-hopReasoning”
‣ FocusesjustonHotpotQA
‣ Addi;onallytriestoadversariallyhardenHotpotagainstthesea8acks.Somelimitedsuccess,butdoesn'tsolvetheproblem
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Ques;onAnsweringwithChains
ChainExtractor
QAmodel(BERT)
FinalAnswerSpan
ReasoningChain
‣Maybewecanstrengthenourmodelstoavoidtheseweaknesses.Forcethemtoexplicitlyextractareasoningchaintomakethembe8er
Q:Whatgovernmentposi2onwasheld…
Sent1 Sent2
…Shebeganherdiploma=ccareer…
AKissforCorlisswas…
ShirleyTempleBlackwasa…
KissandTellisacomedyfilminwhich17-year-oldShirleyTempleactsasCorlissArcher.
Asanadult,sheservedasChiefofProtocoloftheUnitedStates
Sent5
Chenetal.(2019)
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Ques;onAnsweringwithChainsQues%on:Whatgovernmentposi=onwasheldbythewomanwhoportrayedCorlissArcherinthefilmKissandTell?Answer:ChiefofProtocol
ShirleyTempleBlackwasanAmericanactress,businesswoman,anddiplomat…
Asanadult,sheservedastheChiefofProtocoloftheUnitedStates…
Shebeganherdiploma=ccareerin1969,whensherepresented…
KissandTellisafilminwhich17-year-oldShirleyTempleactsasCorlissArcher.
“AKissforCorliss”isasequeltothefilm“KissandTell”.
ItstarsShirleyTempleinherfinalstarringrole…
DO
C 1
DO
C 2
DO
C 3
SharedEn;ty
ShirleyTemple
CorlissArcher
ReasoningChain1
In-DocCoref
‣ Strongconnec;onbetweentheen;;esusedhereChenetal.(2019)
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Ques;onAnsweringwithChains
SharedEn;ty
ShirleyTemple
ReasoningChain2
In-DocCoref
KissandTell
‣Morespecula;vethantheotherchainbuts;llleadstotheanswer
Ques%on:Whatgovernmentposi=onwasheldbythewomanwhoportrayedCorlissArcherinthefilmKissandTell?Answer:ChiefofProtocol
ShirleyTempleBlackwasanAmericanactress,businesswoman,anddiplomat…
Asanadult,sheservedastheChiefofProtocoloftheUnitedStates…
Shebeganherdiploma=ccareerin1969,whensherepresented…
KissandTellisafilminwhich17-year-oldShirleyTempleactsasCorlissArcher.
“AKissforCorliss”isasequeltothefilm“KissandTell”.
ItstarsShirleyTempleinherfinalstarringrole…
DO
C 1
DO
C 2
DO
C 3
Chenetal.(2019)
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ChainSupervision
‣ Extractpseudogoldchainsbasedon:
SharedEn;ty
ShirleyTemple
CorlissArcher
In-DocCoref
‣Within-documentcoreference:wedon’trunacoreferencesystembutinsteadlinkallsentenceswithinaparagraph
‣ Shareden;;es:enableconnec;onsbetweendifferentsources
‣ Giventhesechains,welearnamodeltoextractthem.Attest2me,noannota2onsareneeded
Chenetal.(2019)
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ChainExtrac;onandQA‣ ParagraphsareencodedwithBERTtocomputesentencerepresenta;ons
BERT
BERT
‣ Apointernetworkselectsasequenceofsentences
s3
s3
s7
s3
STOP
‣ AfinalBERTmodel thenextractsananswerspanfromoneormorechains
s3 s7
s3 s8
s1 s2
BERT Ans
Chenetal.(2019)
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QAResults
‣ HighperformanceonWikiHop(*pastsystemsdidn'tuseBERT)andHotpot‣ AlsolargegainsonhardexamplesinHotpotQA(ourmodelfrompart1couldnotfindanswersinasinglehop)
WikiHop(English)
50
60
70
80
90
76.571.470.970.669.067.6
50
60
70
80
90
74.169.768.169.6
HotpotQA(English)
DecompRC QFE Ours
Accuracy
F1
GCN BAG CFC JDReader DynSAN Ours DFGN
‣ Ongoingwork:howcanreasoningchainsbetakenbelowthesentencelevelandbemorestrongly;edtointerpretablelogicalinference?
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NewTypesofQA
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DROP
Duaetal.(2019)
‣ Ques;ontypes:subtrac;on,comparison(whichdidhevisitfirst),coun;ngandsor;ng(whichkickerkickedmorefieldgoals),
‣ Invitesadhocsolu;ons(structurethemodelaroundpredic;ngdifferencesbetweennumbers)
‣ Onethreadofresearch:let’sbuildQAdatasetstohelpthecommunityfocusonmodelingpar;cularthings
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Mul;QA
TalmorandBerant(2019)
‣MaybeweshouldjustlookatlotsofQAdatasetsinstead?
‣ BERTtrainedonSQuADgets
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Narra;veQA
Kočiskýetal.(2017)
‣ Humansseeasummaryofabook:…Peter’sformergirlfriendDanaBarre`hashadason,Oscar…
‣ Ques;on:HowisOscarrelatedtoDana?
‣ Answeringtheseques;onsfromthesourcetext(notsummary)requirescomplexinferencesandisextremelychallenging;noprogressonthisdatasetin2years
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Takeaways
‣ModelscanoeenworkwellforoneQAtaskbutdon’tgeneralize
‣Wes;lldon’thave(solvable)QAsecngswhichseemtorequirereallycomplexreasoningasopposedtosurface-levelpa8ernrecogni;on
‣ LotsofproblemswithcurrentQAsecngs,lotsofnewdatasets