CS388:NaturalLanguageProcessing

GregDurre8

Lecture22:Ques;on 
Answering2

Recall:SQuAD

‣ Single-document,single-sentenceques;on-answeringtaskwheretheanswerisalwaysasubstringofthepassage

Rajpurkaretal.(2016)

‣ Predictstartandendindicesoftheanswerinthepassage

Recall:Bidirec;onalA8en;onFlow

Seoetal.(2016)

Eachpassagewordnow“knowsabout”thequery

Recall:QAwithBERT

Devlinetal.(2019)

WhatwasMarieCuriethefirstfemalerecipientof?[SEP]OneofthemostfamouspeopleborninWarsawwasMarie…

‣ Predictstartandendposi;onsofanswerinpassage‣ NoneedforcrazyBiDAF-stylelayers

Recall:SQuADSOTA

‣ HarderQAsecngsareneeded

‣ Performanceisverysaturated

ThisLecture

‣ Retrieval-basedQA/mul;-hopQA

‣ ProblemsinQA,especiallyrelatedtoanswertypeoverficng

‣ NewQAfron;ers

ProblemsinQA

AdversarialSQuAD‣ SQuADques;onsareoeeneasy:“whatwasshetherecipientof?”passage:“…recipientofNobelPrize…”

JiaandLiang(2017)

AdversarialSQuAD

WhatwasMarieCuriethefirstfemalerecipientof?[SEP]…firstfemalerecipientoftheNobelPrize…

‣ BERTeasilylearnssurface-levelcorrespondenceslikethiswithself-a8en;on

AdversarialSQuAD‣ SQuADques;onsareoeeneasy:“whatwasshetherecipientof?”passage:“…recipientofNobelPrize…”

JiaandLiang(2017)

‣ Canwemakethemharderbyaddingadistractoranswerinaverysimilarcontext?

‣ Takeques;on,modifyittolooklikeananswer(butit'snot),thenappendittothepassage

AdversarialSQuAD

JiaandLiang(2017)

‣ Distractor“looks”moreliketheques;onthantherightanswerdoes,evenifen;;esarewrong

WeaknesstoAdversaries

JiaandLiang(2017)

‣ Performanceofbasicallyeverymodeldropstobelow60%(whenthemodeldoesn'ttrainonthese)

‣ BERTvariantsalsoweaktothesekindsofadversaries

‣ Unlikeotheradversarialmodels,wedon’tneedtocustomizetheadversarytothemodel;thissinglesentencebreakseverySQuADmodel

UniversalAdversarial“Triggers”

Wallaceetal.(2019)

‣ Adding“whyhowbecausetokillamericanpeople”causesSQuADmodelstoreturnthisanswer10-50%ofthe;mewhengivena“why"ques;on

‣ Similara8acksonotherques;ontypeslike“who”

‣ SimilartoJiaandLiang,butinsteadaddthesameadversarytoeverypassage

HowtofixQA?‣ Be8ermodels?

‣ Be8erdatasets

‣ Butamodeltrainedonweakdatawilloeens;llbeweaktoadversaries‣ TrainingonJia+Liangadversariescanhelp,butthereareplentyofothersimilara8ackswhichthatdoesn'tsolve

‣ Sameques;onsbutwithmoredistractorsmaychallengeourmodels

‣ HarderQAtasks‣ Askques;onswhichcannotbeansweredinasimpleway

‣ Nextup:retrieval-basedQAmodels

‣ Aeerwards:mul=-hopQAandotherQAsecngs

RetrievalModels

Open-domainQA

‣ SQuAD-styleQAisveryar;ficial,notreallyarealapplica;on

‣ RealQAsystemsshouldbeabletohandlemorethanjustaparagraphofcontext—theore;callyshouldworkoverthewholeweb?

Q:WhatwasMarieCurietherecipientof?

MarieCuriewasawardedtheNobelPrizeinChemistryandtheNobelPrizeinPhysics…

MotherTeresareceivedtheNobelPeacePrizein…

CuriereceivedhisdoctorateinMarch1895…Skłodowskareceivedaccoladesforherearlywork…

Open-domainQA

‣ SQuAD-styleQAisveryar;ficial,notreallyarealapplica;on

‣ RealQAsystemsshouldbeabletohandlemorethanjustaparagraphofcontext—theore;callyshouldworkoverthewholeweb?

‣ QApipeline:givenaques;on:

‣ RetrievesomedocumentswithanIRsystem

‣ ZeroinontheanswerinthosedocumentswithaQAmodel

‣ Thisalsointroducesmorecomplexdistractors(badanswers)andshouldrequirestrongerQAsystems

DrQA

Chenetal.(2017)

‣ Howoeendoestheretrievedcontextcontaintheanswer?(usesLucene)

‣ FullretrievalresultsusingaQAmodeltrainedonSQuAD:taskismuchharder

RetrievalwithBERT

Leeetal.(2019)

‣ Canwedobe8erthanasimpleIRsystem?

‣ EncodethequerywithBERT,pre-encodeallparagraphswithBERT,queryisbasicallynearestneighbors

Problems

Leeetal.(2019)

‣ManySQuADques;onsarenotsuitedtothe“open”secngbecausethey’reunderspecified

‣ SQuADques;onswerewri8enbypeoplelookingatthepassage—encouragesaques;onstructurewhichmimicsthepassageanddoesn’tlooklike“real”ques;ons

‣WheredidtheSuperBowltakeplace?

‣WhichplayerontheCarolinaPantherswasnamedMVP?

NaturalQues;ons

Kwiatkowskietal.(2019)

‣ Ques;onsarosenaturally,unlikeSQuADques;onswhichwerewri8enbypeoplelookingatapassage.Thismakesthemmuchharder

‣ ShortanswerF1s<60,longanswerF1s

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

Mul;-hopReasoning

TheOberoifamilyisanIndianfamilythatisfamousforitsinvolvementinhotels,namelythroughTheOberoiGroup

Ques%on:TheOberoifamilyispartofahotelcompanythathasaheadofficeinwhatcity?

TheOberoiGroupisahotelcompanywithitsheadofficeinDelhi.

…

…

Doc1

Doc2

Sameen;ty

Sameen;ty

ExamplepickedfromHotpotQA[Yangetal.,2018]

Thisisanidealizedversionofmul;-hopreasoning.Domodelsneedtodothistodowellonthistask?

Mul;-hopReasoning

TheOberoifamilyisanIndianfamilythatisfamousforitsinvolvementinhotels,namelythroughTheOberoiGroup

Ques%on:TheOberoifamilyispartofahotelcompanythathasaheadofficeinwhatcity?

TheOberoiGroupisahotelcompanywithitsheadofficeinDelhi.

…

…

Doc1

Doc2

ExamplepickedfromHotpotQA(Yang2018)

Modelcanignorethebridgingen;tyanddirectlypredicttheanswer

Highlexicaloverlap

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]

Inves;ga;on

Canamodeliden;fytheanswerwithonlyasetofcandidates?

Canamodeliden;fywheretheanswerisinasinglehop?

Governmentposi=on ChiefofProtocol,actress,singer

OberoiFamily Delhi

ChenandDurre8(2019)

FindingtheanswerdirectlyQues2on:Whatgovernmentposi;onwasheldbythewomanwhoportrayedCorlissArcherinthefilmKissandTell?

KaushikandLipton(2018)

ChiefofProtocolbusinesswoman…actress

MeetCorlissArcherisanAmericantelevisionsitcomthatairedonCBS…

ShirleyTempleBlackwasanAmericanactress,businesswoman,andsinger…

KissandTellisacomedyfilminwhich17-year-oldShirleyTempleactsasCorlissArcher.

Asanadult,sheservedasChiefofProtocoloftheUnitedStatesDoc1

Doc2

Doc3

NoContextBaseline

DotProduct

Ques%on:Whatgovernmentposi=onwasheldbythewomanwhoportrayedCorlissArcherinthefilmKissandTell?

ChiefofProtocol businesswoman actress

Ques;onEncoder

AnswerEncoder

...

ChiefofProtocol0.7

businesswoman0.2

actress0.1

ChenandDurre8(2019)

Accuracy

30

50

70

59.3

67.466.464.8

42.9

38.8

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)

Inves;ga;on

Canamodeliden;fytheanswerwithonlyasetofcandidates?

Canamodeliden;fywheretheanswerisinasinglehop?

Governmentposi=on ChiefofProtocol,actress,singer

OberoiFamily Delhi

ChenandDurre8(2019)

SentenceFactoredModel

Findtheanswerbycomparingeachsentencewiththeques;onseparately!

Ques%on:TheOberoifamilyispartofahotelcompanythathasaheadofficeinwhatcity?

TheOberoiGroupisahotelcompanywithitsheadofficeinDelhi.

Doc2

FutureFibreTechnologiesafibertechnologiescompany…

Doc3

TheOberoifamilyisanIndianfamilythatis…

Doc1

ChenandDurre8(2019)

SentenceFactoredModel

TheOberoifamily…whatcity?

TheOberoiGroup…inDelhi.

FutureFibreTechnologiesisafibre…

TheOberoifamily…

Answerpredic;on:Delhi ‣Soemaxoverallsentencesistheonlycross-sentenceinterac;on

BiDAF BiDAFBiDAF

ChenandDurre8(2019)

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)

OtherWork

‣ Minetal.ACL2019“Composi;onalQues;onsdonotNecessitateMul;-hopReasoning”

‣ FocusesjustonHotpotQA

‣ Addi;onallytriestoadversariallyhardenHotpotagainstthesea8acks.Somelimitedsuccess,butdoesn'tsolvetheproblem

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)

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)

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)

ChainSupervision

‣ Extractpseudogoldchainsbasedon:

SharedEn;ty

ShirleyTemple

CorlissArcher

In-DocCoref

‣Within-documentcoreference:wedon’trunacoreferencesystembutinsteadlinkallsentenceswithinaparagraph

‣ Shareden;;es:enableconnec;onsbetweendifferentsources

‣ Giventhesechains,welearnamodeltoextractthem.Attest2me,noannota2onsareneeded

Chenetal.(2019)

ChainExtrac;onandQA‣ ParagraphsareencodedwithBERTtocomputesentencerepresenta;ons

BERT

BERT

‣ Apointernetworkselectsasequenceofsentences

s3

s3

s7

s3

STOP

‣ AfinalBERTmodel 
thenextractsananswerspanfromoneormorechains

s3 s7

s3 s8s1 s2

BERT Ans

Chenetal.(2019)

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?

NewTypesofQA

DROP

Duaetal.(2019)

‣ Ques;ontypes:subtrac;on,comparison(whichdidhevisitfirst),coun;ngandsor;ng(whichkickerkickedmorefieldgoals),

‣ Invitesadhocsolu;ons(structurethemodelaroundpredic;ngdifferencesbetweennumbers)

‣ Onethreadofresearch:let’sbuildQAdatasetstohelpthecommunityfocusonmodelingpar;cularthings

Mul;QA

TalmorandBerant(2019)

‣MaybeweshouldjustlookatlotsofQAdatasetsinstead?

‣ BERTtrainedonSQuADgets