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1、TheRWTHSystemCombinationSystemforWMT2009GregorLeusch,EvgenyMatusov,andHermannNeyRWTHAachenUniversityAachen,GermanyAbstractRWTHparticipatedintheSystemCombi-nationtaskoftheFourthWorkshoponSta-tisticalMachineTranslation(WMT2009).Hypothesesfrom9German!EnglishMTFigure1:Thesyste
2、mcombinationarchitecture.systemswerecombinedintoaconsen-sustranslation.Thisconsensustransla-systempriorweightsandalanguagemodel(LM).tionscored2.1%betterinBLEUand2.3%ThesinglebestpathinthisCNthenconstitutesthebetterinTER(abs.)thanthebestsin-consensustranslation.glesystem.In
3、addition,cross-lingual2.1WordAlignmentoutputfrom10French,German,andSpanish!EnglishsystemswascombinedTheproposedalignmentapproachisastatisticalintoaconsensustranslation,whichgaveone.Ittakesadvantageofmultipletranslationsforanimprovementof2.0%inBLEU/3.5%inawholecorpustocompu
4、teaconsensustranslationTER(abs.)overthebestsinglesystem.foreachsentenceinthiscorpus.Italsotakesad-vantageofthefactthatthesentencestobealigned1Introductionareinthesamelanguage.ForeachsourcesentenceFinthetestcorpus,TheRWTHapproachtoMTsystemcombinationweselectoneofitstranslat
5、ionsEn;n=1;:::;M;isarefinedversionoftheROVERapproachinastheprimaryhypothesis.Thenwealignthesec-ASR(Fiscus,1997),withadditionalstepstocopeondaryhypothesesEm(m=1;:::;M;n6=m)withreorderingbetweendifferenthypotheses,andwithEntomatchthewordorderinEn.Sinceitistousetruecasinginfor
6、mationfromtheinputhy-notclearwhichhypothesisshouldbeprimary,i.e.potheses.Thebasicconceptoftheapproachhashasthe“best”wordorder,weleteveryhypothesisbeendescribedbyMatusovetal.(2006).Severalplaytheroleoftheprimarytranslation,andalignimprovementshavebeenaddedlater(Matusovetall
7、pairsofhypotheses(En;Em);n6=m.al.,2008).ThisapproachincludesanenhancedThewordalignmentistrainedinanalogytoalignmentandreorderingframework.Incon-thealignmenttrainingprocedureinstatisticalMT.trasttoexistingapproaches(JayaramanandLavie,Thedifferenceisthatthetwosentencesthatha
8、ve2005;Rostietal.,2007),thecontextofthewholetobealignedareinthesamelanguage.Weusethecorpu
