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1、CHAPTER20DataAnalysisandMiningPracticeExercises20.1Describebenefitsanddrawbacksofasource-drivenarchitectureforgatheringofdataatadatawarehouse,ascomparedtoadestination-drivenarchitecture.Answer:Inadestination-drivenarchitectureforgatheringdata,datatransfersfromthedatasourcestothedata-warehousearebased
2、ondemandfromthewarehouse,whereasinasource-drivenarchitecture,thetransfersareinitiatedbyeachsource.Thebenefitsofasource-drivenarchitectureare•Datacanbepropagatedtothedestinationassoonasitbecomesavailable.Foradestination-drivenarchitecturetocollectdataassoonasitisavailable,thewarehousewouldhavetoprobet
3、hesourcesfrequently,leadingtoahighoverhead.•Thesourcedoesnothavetokeephistoricalinformation.Assoonasdataisupdated,thesourcecansendanupdatemessagetothedestinationandforgetthehistoryoftheupdates.Incontrast,inadestination-drivenarchitecture,eachsourcehastomaintainahistoryofdatawhichhavenotyetbeencollec
4、tedbythedatawarehouse.Thusstoragerequirementsatthesourcearelowerforasource-drivenarchitecture.Ontheotherhand,adestination-drivenarchitecturehasthefollowingadvantages.•Inasource-drivenarchitecture,thesourcehastobeactiveandmusthandleerrorconditionssuchasnotbeingabletocontactthewarehouseforsometime.Iti
5、seasiertoimplementpassivesources,andasingleactivewarehouse.Inadestination-drivenarchitecure,eachsourceisrequiredtoprovideonlyabasicfunctionalityofexecutingqueries.•Thewarehousehasmorecontrolonwhentocarryoutdatagath-eringactivities,andwhentoprocessuserqueries;itisnotagood12Chapter20DataAnalysisandMin
6、ingideatoperformbothsimultaneously,sincetheymayconflictonlocks.20.2Whyiscolumn-orientedstoragepotentiallyadvantageousinadatabasesystemthatsupportsadatawarehouse?Answer:NoAnswer20.3Supposethattherearetwoclassificationrules,onethatsaysthatpeoplewithsalariesbetween$10,000and$20,000haveacreditratingofgood
7、,andanotherthatsaysthatpeoplewithsalariesbetween$20,000and$30,000haveacreditratingofgood.Underwhatconditionscantherulesbereplaced,withoutanylossofinformation,byasinglerulethatsayspeoplewithsalariesbet
