《信息科学类专业英语》课件第10章

Lesson10DataWarehouseOverview

(第十课数据仓库概论)

Vocabulary(词汇)ImportantSentences(重点句)QuestionsandAnswers(问答)Problems(问题)

TheworddatawarehousewasfirstdevelopedbyBillInmonintheearly1990s.Hereferredtoitasbeingaintegratedcollectionofinformationthatcouldhelpcompaniesandorganizationsmakebetterdecisions.

Tobeeffective,adatawarehousehadtobeintegrated,subjectoriented,non-volatile,andtimevariant.Inthisarticle,Iwillgooverallthesefactorsindetail.Ifyouarebuildingadatawarehouse,itisimportantforyoutounderstandwhytheyareimportant.

Beingsubjectorientedmeansthatthedatawillprovideinformationaboutaspecificsubjectratherthantheinformationaboutthefunctionsofacompany.Becauseadatawarehouseissubjectoriented,itwillallowyoutoanalyzeinformationthatisconnectedtoaspecificsubject.Beingintegratedmeansthatthedatathatiscollectedwithinthedatawarehousecancomefromdifferentsources,butcanbecombinedintooneunitthatisrelevantandlogical.Havingatime-variantmeansthatalltheinformationwithinthedatawarehousecanbefoundwithagivenperiodoftime.[1]

Itisimportantthattheinformationcontainedwithinadatawarehouseisstable.Whiledatacanbeadded,itshouldneverbedeleted.Thispropertyisreferredtoasbeingnon-volatile.Whenacompanyusesadatawarehousethatisstable,thiswillallowthemtogetabetterunderstandingoftheoperationswithintheircompany.Despitethefactthatthesetermswerefirstcoinedinthe1990s,theyarestillhighlyaccuratetoday.However,itshouldbenotedthatsomedatawarehousesarevolatile.Thereasonforthisisbecausemanymoderndatawarehousesdealwithterabytesofdata.Becausetheymuststoreterabytesofdata,manycompaniesareforcedtodeletesomeoftheirinformationafteracertainperiodoftime.Forinstance,somecompanieswillsystematicallydeletedatathathasreachedthreeyearsofage.Beforeadatawarehousecanbebuilt,thecorrectdatamustbelocated.Generally,theinformationthatwillbeaddedtothewarehousewillcomefromdailyinformationorhistoricalinformation.Thehistoricalinformationmaybestoredinalegacysystem,andischallengingtoextract.

Thedesignofthedatawarehouseisimportantaswell.Itisimportantfordesignerstomakesurethedesignisconsistentwiththequeriesthatwillbeconductedwithinthewarehouse.Todothissuccessfully,itisimportantfordesignerstounderstandthedatabaseschema.Itiscrucialtomakesurethedatawarehouseisdesignedcorrectly,asitisdifficulttorecreatesomeformsofdata.Anotherimportantaspectofdatawarehousesisdataacquisition.Dataacquisitioncanbedefinedastransferringdatafromasourcetothewarehouse.Dataacquisitionisoneofthemostexpensivepartsofbuildingadatawarehouse.ThisprocesswilloftenbeconductedwithanETL(Extracting,TranslatingandLoading)tool.

Asofthistime,therearejustover50ETLtoolsbeingsold.Itmaycostacompanymillionsofdollarsinordertotransferdatafromsourcestothewarehouse.Oncetheinitialdatahasbeentransferredtothedatawarehouse,theprocessmustberepeatedconsistently.Dataacquisitionisacontinuousprocess,andthegoalofacompanyistomakesurethewarehouseisupdatedonaregularbasis.Whenthewarehouseisupdated,itisoftenhardtodeterminewhichinformationinthesourcehaschangedsincethepreviousupdate.Theprocessofdealingwiththisissueiscalledchangeddatacapture.Thisprocesshasbecomeaseparatefield,andthereareanumberofproductscurrentlybesoldtodealwithit.

Itisimportantfordatatobecleanedbeforeitcanbeplacedinthewarehouse.Thedatacleansingprocessisusuallydoneduringthedataacquisitionphase.Anydatathatisplacedinawarehousebeforebeingcleanwillposeadangertothesystem,anditcannotbeused.Thereasonforthisisbecausethedatamaynotbecorrectifitisnotcleaned,andacompanymaymakeincorrectdecisionsbasedonit.Thiscouldleadtoanumberofproblems.Forexample,alltheinformationwithinadatawarehousethatmeansthesamethingmustbestoredinthesameform.Ifthereisinformationthatreads“MS”and“Microsoft”,eventhoughtheymeanthesamething,onlyoneofthemcanbeusedtorecognizetheelementwithinthedatawarehouse.1DataWarehouseTools

Thereareanumberofimportanttoolswhichareconnectedtodatawarehouses,andoneoftheseisdataaggregation.Adatawarehousecanbedesignedtostoreinformationbasedonacertainlevelofdetail.Forexample,youcanstoredatabasedoneachtransaction,oryoucanstoreitbasedonasummary.Theseareexamplesofdataaggregation.Whendataissummarized,thequerieswillmoveatamuchfasterrate.However,someoftheinformationmaybelostduringaquery,andthisinformationmaybeimportantforsolvingacertainproblem.

Beforeyoudecidewhichoneyouwilluse,itisimportanttoweighyouroptionscarefully.Onceyouhavecarriedoutanoperation,youwillneedtorebuildthewarehouseinordertoundoit.Thebestwaytohandlethissituationistomakesurethedatawarehouseisconstructedwithalargeamountofdetail.However,thecostforthiscanbehugedependingonthestorageoptionsyouchoose.Onceyouhavefilledyourdatawarehousewithimportantinformation,youwillwanttousethisdatatohelpyoumakesmartinvestmentdecisions.Thetoolsthatcanallowyoutodothiswillfallunderatopicthatiscalledbusinessintelligence.

Businessintelligenceisafieldwhichisverydiverse.ItiscomprisedofthingssuchasExecutiveInformationSystems,DecisionSupportSystems,andBusinessintelligencecanfurtherbebrokendownintoafieldthatiscalledmulti-dimensionalanalysistools.Thesearetoolsthatwillallowausertoviewdatafromawidevarietyofangles.AquerytoolwillallowausertosendSQLquerieswithinawarehousetolookforresults.Dataminingisalsoafieldthatfallsunderbusinessintelligence,andwillallowyoutolookforpatternsandrelationshipswithinadatawarehouse.

Anothertoolthatisconnectedtodatawarehousesisdatavisualization.Thetoolsthatareusedfordatavisualizationwillpresentvisualmodelsofdata.Thisdatacouldcomeintheformofintricate3Dimages.Thegoalofdatavisualizationistoallowtheusertoviewtrendsinamethodwhichiseasiertounderstandthancomplicatedmodelsthatarebasedoffstatistics.OnetoolthatisallowingthisfieldtoadvanceisVRML,orVirtualRealityModelingLanguage.Inorderfordatawarehousestofunctionproperly,itisalsoimportanttoplaceanemphasisonmetadatamanagement.Metadatacanbedescribedasbeing“informationaboutinformation”.

Metadatamustbemanagedwhendataisacquiredoranalyzed.Metadatawillbeheldinarepository,andcangiveyouimportantinformationaboutmanyofthedatawarehousetools.Theprocessofproperlymanagingmetadatahasbecomeasciencewithinitself.Ifitisdoneproperly,thecompanycangreatlybenefit.Thereasonwhyitisimportantisbecauseitcanalloworganizationstoanalyzethechangesthatoccurwithindatabasetables.Thisisatoolthatplaysanimportantpartoftheconstructionofadatawarehouse.

Datawarehousingisafieldwhichissomewhatcomplicated.Therearemanyvendorswhoareattemptingtoadvertisethetools,butthecostandcomplexityinvolvedwiththeproductshasnotallowedthemtobeusedbyalargenumberofcompanies.Anycompanythatisthinkingofusingdatawarehousesmustmakesuretheyhavetakenthetimetoreviewandunderstandthetechnology.Itcanonlybeusefulifyouknowhowtouseit.Onceyouunderstandandacquirethetechnology,itispossibleforyoutogainapowerfuladvantageoveryourcompetitors.Thishasmadedatawarehousesattractivetomanycompanies.

Oneofthebiggestadvantagestodatawarehousesisthattheyallowyoutostoreinformationthatyoucanusetoimprovethemarketingstrategiesofyourcompany.Notonlycanyouimprovethemarketingstrategies,butyouwillalsobeabletomakestrategicdecisionsbasedontheinformationyouhavecompiledandorganized.Withtechniquessuchasdatamininganddatavisualization,youwillbeabletodiscoverimportantpatternsthatyoudidn’tknowexisted.Thepatternsthatyoudiscovercanallowyourcompanytoearnlargeprofits.2DataWarehousingMethods

Mostorganizationsagreethatdatawarehousesareausefultool.Theybenefitfromtheabilitytostoreandanalyzedata,andthiscanallowthemtomakesoundbusinessdecisions.Itisalsoimportantforthemtomakesurethecorrectinformationispublished,anditshouldbeeasytoaccessbythepeoplewhoareresponsibleformakingdecisions.

Therearetwoelementsthatmakeupthedatawarehouseenvironment,andthesearepresentationandstaging.Thestagingcouldalsobeknownastheacquisitionarea.ItiscomposedofETLoperations,andoncethedatahasbeenprepared,itwillbesenttothepresentationarea.

Whenthedataisplacedwithinthepresentationarea,anumberofprogramswillanalyzeandreviewit.Whilemanyorganizationsagreeontheoverallgoalofdatawarehouses,theapproachestobuildingthemmaydiffer.Attemptingtousedatamartsaloneisnotagoodapproach,becausetheyaregearedtowardsdepartments.Inadditiontothis,attemptingtousedatamartsalonewillbeinefficient,andyouwillrunintoanumberoflongtermproblems.Therearetwotechniquesforbuildingdatawarehousesthathavebecomeverypopular.ThesearetheKimballBusArchitectureandtheCorporateInformationFactory.

WiththeKimballtechnique,theroughdatawillbetransformedandrefinedwithinthestagingarea.Itisimportanttomakesurethedataisproperlyhandledduringthisstep.Duringthestagingprocess,theroughdatawillbepulledfromthesourcesystems.Whilesomeofthestagingprocessesmaybecentralized,otherswillbedistributed.Thepresentationareawillhaveadimensionalstructure,andthismodelwillholdthesameinformationasastandardmodel.However,itwillbeeasiertouse,anditwilldisplayinformationthatissummarized.

Adimensionalmodelwillbecreatedbyabusinessoperation.Departmentswithintheorganizationdonotplayaroleinthis.Thedatawillbepopulatedonceitisplacedwithinthedimensionalwarehouse,andisnotdependentonthevariousdepartmentsthatmaycomposeanorganization.Whenbusinessprocesseshavebeendevelopedwithinthewarehouse,thesystemwillbecomehighlyefficient.ThenextpopulardatawarehouseapproachthatyouwillwanttobecomefamiliarwithistheCorporateInformationFactory.AnothernameforthistechniqueistheEDWapproach.Thedatathatisextractedfromthesourcewillbecoordinated.

WithintheCIF,astandarddatawarehouseisusedtoholddatarepositories,anditmayalsohavespecificdatawarehouseswhicharedesignedfordatamining.Thedatamartsmaybedesignedforspecificdepartments,andtheymayhavesummarydatawhichisintheformofadimensionalstructure.Theatomicdatamaybeobtainedfromthestandarddatawarehouse.Whiletherearesomesimilaritiesbetweenthesetotechniques,therearesomenotabledifferencesaswell.

Oneoftheprimarydifferencesbetweenthesetwotechniquesisthenormalizeddatafoundation.WiththeKimballapproach,thedatastructuresthatmustbeobtainedbeforethedimensionalpresentationwillbedependentonthesourcedataandtransformation.Inmostcases,theduplicatestorageofdataisnotrequiredinbothdimensionalandnormalizedfoundations.Manyofthepeoplewhochoosetouseanormalizeddatastructurebelievethatitisfasterthanthedimensionalstructure,buttheyoftenfailtotakeETLintoconsideration.

Anotherthingthatseparatesthetwodatawarehouseapproachesisthemanagementofatomicdata.WiththeCIF,atomicdatawillbestoredwithinanormalizeddatawarehouse.Incontrast,theKimballmethodstatesthattheatomicdatashouldbeplacedwithinadimensionalstructure.Whenthedataisplacedwithinadimensionalstructure,itcanbesummarizedinawidevarietyofdifferentways.

Itisimportanttomakesuretheinformationyouhaveisdetailedsothatuserswillbeabletoaskrelevantquestions.Whilemostuserswillnotplaceanemphasisonthedetailsofoneatomictransaction,theymaywantasummaryofalargenumberoftransactions.Itisimportantforthemtohavethedetailssothattheywillbeabletoanswerimportantquestions.Theapproachthatyouchooseshouldbetheonewhichbestservestheneedsofyourcompany.3DataWarehouseDesignStrategies

Tobuildaneffectivedatawarehouse,itisimportantforyoutounderstanddatawarehousedesignprinciples.Ifyourdatawarehouseisnotbuiltcorrectly,youcanrunintoanumberofdifferentproblems.

Thepropermethodsforbuildingapowerfuldatawarehousearebasedoninformationtechnologytactics.Firstoff,itisimportantthatyouandyourorganizationunderstandtheimportanceofhavingadatawarehouse.Ifworkersfeelthatadatawarehouseisunnecessary,theymaynotuseit,andthiscouldcauseconflicts.Everyoneinyourorganizationshouldunderstandtheimportanceofusingthesystem.

Afteryouhavegotyourcolleaguesbehindtheconceptofusingadatawarehouse,youwillwanttonextfocusondataintegrity.Youwillwanttoavoiddesigningadatawarehousethatwillloaddatathatisnotconsistent.Itisalsoimportanttoavoidcreatingadatabasethatwillreplicatedata.Thegoalofyourorganizationshouldbetointegratedataandcreatestandardsthatwillbeusedandfollowed.Afterdataintegrity,youwillnextwanttolookatimplementationefficiency.Thisbasicallymeansthatyouwillwanttodesignatsystemthatissimpletouse.Itdoesn’tmatterhowwelldesignedyourdatawarehouseisifyourworkershaveahardtimeusingit.

Ifyourworkershaveahardtimeusingthedatawarehouse,itwillslowdownthespeedandproductivityofyouroperation.Whenitcomestocreatingadatawarehouse,youwillwanttomakeitassimpleaspossible.Allofyourworkersshouldbeabletouseitwithoutproblems.Implementationefficiencyisaprinciplethatnaturallyleadstothenexttopicyouwillwanttofocuson,andthisisuserfriendliness.Thisisaconceptthatisanimportantpartofyourbusiness.Thereasonforthisisbecauseenduserswillnotutilizeaprogramthatistoodifficulttouse.Itisimportantforyoutokeeptheminmind.Useadesignwhichisfriendlyandeasytolearn.

Onceyouhavedesignedadatawarehousethatisuserfriendly,youwillnextwanttolookatoperationalefficiency.Oncethedatawarehousehasbeencreated,itshouldbeabletocarryoutoperationsquickly.Inadditiontothis,itshouldnothaveerrorsorothertechnicalproblems.Whenerrorsortechnicalproblemsdooccur,theyshouldbesimpletofix.Anotherthingyouwillwanttolookatisthecostinvolvedwithsupportingthesystem.Youwillwanttokeepthesecostslowasmuchaspossible.

Thedesignprinciplesthathavebeendiscussedinthisarticlesofararemorerelatedtobusinessthaninformationtechnology.However,thereareanumberofITdesignprinciplesthatyouwillwanttofollow.Oneoftheseisscalability.Thisisaproblemthatmanydatawarehousedesignersruninto.Thebestwaytodealwiththisissueistocreateadatawarehousethatisscalablefromthebeginning.Designitinawaywhichwillallowittosupportexpansionsorupgrades.Youshouldbeabletoadaptittoanumberofdifferentbusinesssituations.Thebestdatawarehousesarethosewhicharescalable.

Thedatawarehousethatyoudesignshouldfallundertheguidelinesofinformationtechnologystandards.EverytoolthatyouusetobuildyourdatawarehouseshouldworkwellwithITstandards.Youwillwanttomakesureitisdesignedinawaythatmakesiteasierforyourworkerstouse.Whilefollowingtheguidelinesinthisarticlewon’tallowyoutoalwaysbesuccessful,itwillgreatlytiptheoddsinyourfavor.Youshouldbewaryofcompaniesthatpromiseyouperfectresultsifyouusetheirdesignmethods.[2]Nomatterhowwelldesignedyourdatawarehouseis,youwillalwaysrunintoproblems.However,followingtherightprincipleswillmaketheproblemseasiertorecognizeandsolve.

Whenitcomestousingadatawarehouse,itisnotamatterof“if”youwillrunintoproblems.Itismatterof“how”and“when”.Whenyourdatawarehouseiswelldesigned,youwillbebetterequippedtosolveanyproblemsyouencounter.

1. warehousen.仓库,货栈。

2. goover受欢迎,获得接受；检查。

3. orientvt.vi.使熟悉,使适应；使朝向；确定位置；朝向；确定方向；使适应n.东方,亚洲。

4. variantn.变体;变种;变型adj.不同的;差别的;变异的;各种各样的。

5. specificadj.明确的,确切的,详尽的；具体的,特有的,特定的；仅限于……的。Vocabulary

6. volatileadj.飞行的,挥发性的,可变的,不稳定的,轻快的,爆炸性的n.有翅的动物,挥发物。

7. scheman.概要,计划,图表，模式。

8. acquisitionn.获得,得到的东西；得到的人,买进。

9. aggregationn.集合,凝聚,集成,集结(作用),集合[成]体,集团。

10. strategyn.战略(学),策略,计谋,作战方针;智谋,手腕strategyandtactics战略与战术。

11. Intricateadj.复杂的,错综的,难以理解的。

12. martn.市场;贸易场所。

13. repositoryn.仓库，储藏所；储物器皿，博物馆；学识渊博的人；受人信赖的人，知己。

14. Stagingn.举行,进行;配置，阶变，级,级组，分段运输;分级法。

15. Populatevt.居住，使人口聚居于;移民于;殖民于人口稠密(稀少)的城市。

[1]Beingsubjectorientedmeansthatthedatawillprovideinformationaboutaspecificsubjectratherthantheinformationaboutthefunctionsofacompany.Becauseadatawarehouseissubjectoriented,itwillallowyoutoanalyzeinformationthatisconnectedtoaspecificsubject.Beingintegratedmeansthatthedatathatiscollectedwithinthedatawarehousecancomefromdifferentsources,butcanbecombinedintooneunitthatisrelevantandlogical.Havingatime-variantmeansthatalltheinformationwithinthedatawarehousecanbefoundwithagivenperiodoftime.ImportantSentences

所谓“面向主题”，就是数据将提供有关一个具体的主题的信息，而不是有关公司运行的信息。由于数据仓库是面向主题的，因此它就允许你分析与具体主题相关的