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1、AmoghAsgekar(06329006)JeevanChalke(06329011)VinayDeshpande(06305001)JubinChheda(06305003)OutlineNLPtasksTypesofdomainadaptationSampleselectionbiasStructuralcorrespondinglearningAdaptationbyfeatureaugmentationConclusionTasksinNLPdomainPOSTaggingAssignPOStagstothewordsinagi
2、ventestcorpus.ParsingConstructastructureoutofthegivensentenceformations.WordsensedisambiguationSelectaparticularmeaningofthewordfromvariouspossibilities.NamedentityrecognitionIdentifyingnamedentities(names,addressetc)fromagivencorpus.DomainAdaptationThepre-mentionedtasksar
3、eperformedby“learning”fromacorpusandthenapplyingtheknowledgetoclassifythetestinstances.Incasethetrainingdistributionsandtestdistributionsaredifferent,thentheclassifiertendstoperformerroneously.Insuchcases,classifierneedstobedomainadaptedtoperformaccuratelyonboththedomains.APOSt
4、aggingtaskConsiderthefollowingexample:-LearnerhasaccesstoLabeleddataSrandomlysampledfromthetrainingdistributionPS.UnlabelledsampleTsampledfromanunknowntestdistributionPT.TaskofthelearneristopredictslabelsofpointsgeneratedandlabeledaccordingtoP.TTypesofDomainAdaptationAnalys
5、ethecausesfordomaindivergenceandmodelthemintothelearnerSampleselectionbiasDiscoverthedivergenceofthedistributionsduringtrainingStructuralCorrespondenceLearningFeatureAugmentationModelSampleSelectionBiasWhatisSampleSelectionBias?Samples(x,y,s)aredrawnindependentlyfromadomain
6、(X×Y×S)withdistributionD.Sisabinaryspace.Ifs=1,thatinstanceisselected.Fourcasesofdependenceof(x,y)ons:1.s⊥xands⊥y2.s⊥y
7、x3.s⊥x
8、y4.sdependsonbothxandySampleSelectionBiasCorrectionCase:s⊥y
9、xi.e.Thesub-domainselectiondependsonlyonthewordsandnotontheirPOS-tags.NowifDistheoriginaldi
10、stributionofdomainandD’isthedistributionofselectedsub-domainthen,wecanconvertfromonedomaintootherusingamultiplierPr(s=)1β(X)=Pr(s=
11、1X)Thus,D(x,y,s)=β(X)*D’(x,y,s)•ThepriorprobabilitiesPr(s=1)andPr(s=1
12、x)mustbeknown.•Pr(s=1
13、x)shouldbenon-zeroforeachxi.e.atleastoneinstanceofeachwor
14、dshouldbeselected.SampleSelectionBiasinP
