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1、Control-BasedQualityAdaptationinDataStreamManagementSystemsYi-ChengTu1,MohamedHefeeda2,YuniXia1,SunilPrabhakar1,andSongLiu11PurdueUniversity,WestLafayette,IN47906,U.S.A.2SimonFraserUniversity,Surrey,BC,CanadaAbstract.UnlikeprocessingsnapshotqueriesinatraditionalDBMS,theprocessingofcon
2、tinuousqueriesinadatastreammanagementsystem(DSMS)needstosatisfyqualityrequirementssuchasprocessingdelay.Whenthesystemisoverloaded,qualitydegradessignificantlythusloadsheddingbecomesnecessary.Maintainingthequalityofqueriesisadif-ficultproblembecauseboththeprocessingcostanddataarrivalrate
3、arehighlyunpredictable.Weproposeaqualityadaptationframeworkthatadjuststheapplicationbehaviorbasedonthecurrentsystemsta-tus.Weleveragetechniquesfromtheareaofcontroltheoryindesigningthequalityadaptationframework.Oursimulationresultsdemonstratetheeffectivenessofthecontrol-basedqualityadap
4、tationstrategy.Com-paringtosolutionsproposedinpreviousworks,ourapproachachievessignificantlybetterqualitywithlesswasteofresources.1IntroductionThepastfewyearshavewitnessedtheemergenceofapplicationssuchasnetworkmonitoring,financialdataanalysis,location-basedservices,andsensornetworksinwh
5、ichinformationnaturallyoccursintheformofcontinuousdatastreams.Theseapplicationsdonotfitinthedatamodelandqueryingparadigmoftra-ditionalDatabaseManagementSystems(DBMSs).Datastreammanagementsystems(DSMSs)suchasAurora[1],STREAM[2],andTelegraphCQ[3]arebuiltfordatamanagementandqueryprocessin
6、ginthepresenceofmultiple,continuous,andtime-varyingdatastreams.Insteadofbeingstoredinadvanceondisks,streamingdataelementsarriveon-lineandstayonlyforalimitedtimeperiodinmemory.Consequently,aDSMShastohandlethedataelementsbeforethebufferisoverwrittenbynewincomingdataelements.Processingofd
7、atastreamsbringsgreatchallengestoDBMSdesignfortwomajorreasons.First,streamdataarecontinuouslygeneratedinlargevolumesbyexternalsourcessuchasasensornetwork.Second,thedataareoftencollectedfromremotesitesandarepronetolossanddelayinmostcases.Fromtheappli-cationspointofview,queriestodatastr
8、eamsa
