Playout management in multimedia database systems

PLAYOUTMANAGEMENTINMULTIMEDIADATABASESYSTEMSPLAYOUTMANAGEMENTINMULTIMEDIADATABASESYSTEMSHeikoTHIMMWolfgangKLASGMD-GermanNationalResearchCenterforInformationTechnologyIPSI-IntegratedPublicationandInformationSystemsInstituteDarmstadt,GermanyKLUWERACADEMICPUBLISHERSBoston/London/DordrechtCONTENTS1PLAYOUTMANAGEMENTINMULTIMEDIADATABASESYSTEMS11.1Introduction11.2PlayoutManagement41.3PlayoutManagementforMultimediaDatabases71.4TheAMOSApproach161.5PlayoutManagementinDistributedMultimediaDatabaseSystems261.6AHighlyFlexibleRAPM-Scheme391.7Conclusion55REFERENCES57v1PLAYOUTMANAGEMENTINMULTIMEDIADATABASESYSTEMS1.1INTRODUCTIONThepresenceofmultiplemultimediadatastreams,e.g.,anaudiodatastreaminconjunctionwithseveralvideodatastreamswithinacomplexadvertisementshow,whichpresentationmustproceedinamutuallysynchronizedmanner,isoneoftheuniquefeaturesthatdistinguishesdigitalmultimediadatafromtra-ditional,conventional,alphanumericdata.Sampleapplicationsinwhichthispropertyofdigitalmultimediaisespeciallyimportantareelectronicpublishing,digitallibraries,computer-basedtrainingorteaching(edutainment),advertise-ment,entertainment,andinfotainment.Here,toformmodularlystructuredpresentations,multimediainformationis\gluedtogetherbydesigners(i.e.,presentationauthors)inapreorchestrationphase.Whilesomestandardsrele-vantforthisphasesuchasSGML/HyTime[18]orMHEG[30]aremoreorientedtowardsmultimedia/hypermediadocuments,otherssuchasPREMO[17]andScriptX[47]emphasizemoretime-basedmultimediapresentations.Theresultofthisphaseisapredened/preorchestratedmultimediapresentationforwhichitisassumedthatitsrealizationisrequestedmanytimesbymanydierent(possiblysimultaneous)users.Manymultimediaapplicationdomainssuchasthosementionedbeforeneedtosupportapoolofsuchpreorchestratedmul-timediapresentations.Supportofuserinteractionsisanimportantpropertytobeprovidedwithinthiscontext(\interactivemultimedia).Itprovidesforusersexibilityinpresentationcontrolbyoeringthepossibilitytoadaptthepresentationrealizationphasetotheindividualneeds.Playoutmanagement,ingeneral,isthetaskthatdealswiththerealizationofsucharbitrarypreorchestratedinteractivemultimediapresentations.Itman-agesthepresentationrealizationphasebytakingcareofthenecessarysystem12Chapter1tasksandtheirinterdependenciesaccordingtothepresentationspecication.Thesesystemtasksarethedevicemanagement,thedatastreamhandling,theenforcementofthesynchronizationconstraints,andthehandlingofrandomuserinteractions.Severalreasonsmotivatetheusageofamultimediadatabase(system)withinthiscontext.Thetypicaldatabaseproperties(e.g.,datasharing,persistency,durability,consistency)providesignicanteaseforthemanagementoftheinfor-mation,application-specicpresentationsarecomposedof.Arichdatamodelwhichprovidesmodellingconstructsfortherepresentationofmultimediapre-sentationsallowsforane-grainedandpowerfulmodellingofmultimediain-formation.Sincethepresentationsarecreatedformultipleandsimultaneoususagebymanydierentusers,propersupportformulti-useraccesscanobvi-ouslybeprovidedbyadatabasemanagementsystem.Consideringboth,thefactthatmanymultimediaapplicationsneedplayoutmanagementandthebenetsoftheusageofamultimediadatabasefortheseapplications,thischapteraddressesplayoutmanagementformultimediadatabases.Afteradescriptionofplayoutmanagementfromageneralpointofview,wediscussalternativesolutionsforaframeworkinwhichplayoutmanagementisprovidedforamultimediadatabase.Amajorissuerelatedtothisistoidentifythecomponentsoftheentiresystemandtheirfunctionalityneededtoperformtheplayoutmanagementtask.Basedontheevaluationofalternativeapproaches,wemotivatethatmultime-diadatabasemanagementsystemsshouldperformtheplayoutmanagementbyprovidinganintegratedgenericplayoutmanagementservice.Inanalogytotheprovisionof,e.g.,physicaldataindependency,\playoutmanagementindependencyisprovidedtoo.Thatis,theplayoutmanagementserviceofthemultimediadatabasemanagementsystemmanagestheoutputdevicesin-volved,handlesthedatastreams,enforcesthesynchronizationconstraints,han-dlesrandomuserinteractions,and(fordistributedsystems)evenadaptsthepresentationparameterstothechangingcharacteristicsoftheoverallsystemenvironment.Fromourperspective,thisisanaturaladjustmentofdatabasemanagementsystemfunctionalitytothenewrequirementsofmultimediaap-plications.Thisallowsdeveloperstofocusontheapplicationspecicproblemsandrelievesthemfromthetaskofencodingpresentationfunctionalityorthecouplingofapresentationtool.Thegeneralgoalistoachievethatstorage,retrieval,buermanagement,transport(overapossiblyhigh-speednetwork),aswellasplayoutmanagementarehandledbyacomprehensivesystem,themultimediadatabasemanagementsystem,byusingproperservicesfrom,e.g.,operatingsystemsandnetworks.Aimingatthisgoal,ecientsolutionsforPlayoutManagementinMultimediaDatabaseSystems3themanagementofthedependenciesamongthesetaskscanbeachievedwith-outcompromisingonthefunctionality.Furthermore,weexpect,thatotherdatabaseinternalcomponentscandealwithmultimediadatamoreoptimallyiftheplayoutmanagementiswellintegratedwiththem.Anexampleofamultimediadatabasesystemwithaninteg