... ..name~_jI.I*1name~whereeachnarne~isasimplename. The path-namespecifiesthat the conceptualcomponentbeingreferencedis the componenthavingsimplenamenarne~whichiscontainedwithin the conceptualcomponentwhosenameisname~_1. The conceptualcomponentname~_~isinturncontainedinname~_2,andsoforth.Componentnameswithinapath-namecanbeseparatedbyeithera“.“ora“*“.Whena“.“isused,itmeansthat the conceptualcomponentof the leftsideof the “.“containsdirectly the componenton the right.Whena“*“isused,theremaybeoneormoreintermediatecomponentsbetween the componenton the leftsideand the oneon the right.Inourquerylanguage,conditionsareusuallyexpressedagainstconceptualcomponentsofdocuments,thatis,aconditionhas the form:“componentrestriction”,wherecomponentis the name(orpath-name)ofaconceptualcomponentandrestrictionisanoperatorfollowedbyanexpression.Thisexpressionmaycontainothercomponentnames.Itshouldbenoticedthatanycomponentname(orpath-name)mayrefertoaconceptualcomponentwhichiscontainedinseveralconceptualcomponents.Forinstance,in the exampleinFig.2,wecouldhavea24conditionof the form:“Namerestriction”. The restrictionappliestobothcomponentswhosepath-namesareSender.NameandReceiver.Name. The problemistodecidehowsuchaconditionissatisfied.Therearefourpossibileinterpretations:(1)Namerestriction=Trueif(Sender.Namerestriction=True)A(~(Receiver.Namerestriction=True))(2)Namerestriction=Trueif(Sender.Namerestriction=True)A(V(R.eceiver.Namerestriction=True))(3)Namerestriction=Trueif(Sender.Namerestriction=True)V(V(Receiver.Namerestriction=True))(4)Namerestriction=Trueif(Sender.Namerestriction=True)V(3(Receiver.Namere8triction=True))Oursystemuses the thirdinterpretation,sinceitis the mostgeneral: the answertoquery(3)contains the answerstoqueries(1),(2),and(3).Thischoicereflects the approachofgivingto the user the mostgeneralanswers,whenthereareambiguitiesin the query.Then, the user,whodidnotknowexactly the typesdefinedin the documentbase,canrefine the theoriginalqueryspecifyingexactly the meaningof the query. The fourdifferentsemantics,inourquerylanguage,canbespecifiedexplicitlyas:(1)Sender.NamerestrictionandsomeReceiver.Namerestriction(2)Sender.NamerestrictionandeveryReceiver.Namerestriction(3)Sender.NamerestrictionoreveryReceiver.Namerestriction(4)Sender.NamerestrictionorsomeReceiver.NamerestrictionInadditionto the previoustypesofconditions, the languagemustallowconditionson the existenceofconceptualcomponentswithindocuments.Thisallowsexpressingquerieson the conceptualstructureofdocuments.Thereforewehavedefined the operator“with”.Aconditioncontaining the “with”operatorhas the form:“withcomponent”.Thisconditionexpresses the factthat the componentwhosename(orpathname)isgivenmustbeaconceptualcomponentof the documentstoberetrieved.Toexpressconditionsthatrequirethataconceptualcomponenthavingnamenarne~iscontainedinaconceptualcomponenthavingnamename,, the path-namename1*name,isused. The “with”operatorisconceptuallyveryimportantinourquerylanguage.While the otheroperatorsallow the definitionofconditionsondata(ie.documentinstance), the “with”operatorallows the definitionofconditiou8onmeta-data(ie.documenttypes).Anexamplequerythatwillbeusedthroughoutthispaperis:finddocumentswhereDocument.Date>/1/1/1987/and(*Sender.Name=“Olivetti”or*ProductYresentationcontains“Olivetti”)and*Product.Descriptioncontains“PersonalComputerl”and(*Address.Country=“Italy”ortextcontains“Italy”)andwith*CompanyLogo;Itshouldbenoticedthatnotypeisspecifiedforthisquery.Aswewillsee,oneof the tasksassociatedwithType-LevelProcessingistodetermine the type(s),ifany,towhich the queryapplies.3.InitialStepsinQueryProcessing The taskofqueryprocessingconsitsofseveralsteps,someofwhichareconcernedwithqueryoptimizationIBERT87I.Inthispaperweconsider the pre-processingsteps,inwhichsomeinitialactivitiesareperformed,suchasqueryparsingandaccessing the typecatalog.Alsoduringthisphase, the queryismodifiedinlightof the typehierarchy.3.1.Parsing The queryisparsedbyaconventionalparser. The parserverifiesthat ... beenchosenbecauseoftheirabilitytostoreinexpensivelylargevolumesofmultimediainformation.Wearestudyingvariousaspectsofqueryprocessinginsuchanenvironmentanalyticallyandexperimentally. The resultsofourinvestigationswillbeincorporatedinoursystemimplementation.Inthisreportweoutlineourresearcheffortsinmultimediaqueryprocessing.IssuesinOpticalDiskBasedMultimediaQueryProcessingIn the environmentdescribedabove,anumberofnewissuesandproblemsinqueryprocessingappear.First,performanceestimatesforretrievalmustbederived.Suchestimateshavetotakeintoaccount the natureof the storagemedia(e.g.,foropticaldisks), the distributionof the lengthsof the objectsin the database, the selectivitiesof the queries(mainlytext-based), the placementof the qualifyingobjectson the disk(blockboundariesmaybecrossed), the interactivenatureof the retrievalofmultimediaobjects,aswellas the characteristicsof the accessmethodsthatMINOSuses.Theseissuesandsomepreliminaryresultsofourstudiesaredescribedinmoredetailbelow.17DECEMBER1986VOL.9NO.4aquarterlybulletinof the Computer Societyof the IEEEtechnicalcommitteeonDatabaseeeriCONTENTSLetterfrom the Editor1G.LohmanIssuesin the OptimizationofaLogicBasedLanguage2R.Krishnamurthy,C.ZanioloOptimizationofComplexDatabaseQueriesUsingJoinIndices10P.ValduriezQueryProcessinginOpticalDiskBasedMultimediaInformationSystems17S.ChristodoulakisQueryProcessingBasedonComplexObjectTypes22E.Bert/no,F.RabittiExtensibleCostModelsandQueryOptimizationinGENESIS30D.BatorySoftwareModularizationwith the EXODUSOptimizerGenerator37G.GraefeUnderstandingandExtendingTransformation—BasedOptimizers44A.Rosenthal,P.He/manSPECIALISSUEONRECENTADVANCESINQUERYOPTIMIZATIONRetrievalPerformanceofCAVOpticalDisksOpticaldiskspresentdifferentperformancecharacteristicsthanmagneticdisks.ForConstantAngularVelocity(CAV)disks,amajorperformancedifferencefrommagneticdisksis the existenceofamirrorwithsmallinertiathatcanbe ... typeTYPE-clause;whereCOND-clause;Oneormoreconceptualtypescanbespecifiedin the TYPEclause. The conditionsexpressedin the queryapplyto the documentsbelongingto the specifiedtypes.If the typesindicatedin the queryhavesubtypes,then the queryappliestoall the documentshavingastypeoneofthesesubtypes.Whennotypeisspecified, the querywillapplytoallpossibledocumenttypes. The conditionsexpressedin the CONDclauseareaBooleancombinationofconditionswhichmustbesatisfiedby the documentsretrieved.Conditionsontextcomponentsandconditionsonattributecomponents,ofdifferenttypes,canbemixedin the CONDclause.Atextconditionon the specialcomponentnamed“text”isappliedto the entiredocument.Inordertoreferenceaconceptualcomponentinadocument,apath-namemustbespecified.Apath-namehas the form:name1I*]name2.I*]....