Lengthy development times programmers must design

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Lengthy Development TimesProgrammers must design their own file formatsExcessive Program Maintenance80% of information systems budgetDate 7/22/2019Chapter 21616Problems with Data DependencyEach application programmer must maintain his/her own dataEach application program needs to include code for the metadata of each fileEach application program must have its own processing routines for reading,inserting, updating, and deleting dataLack of coordination and central controlNon-standard file formats
22/07/20199Date 7/22/2019Chapter 217Problems with Data Redundancy (Duplication of Data)Waste of space to have duplicate dataCauses more maintenanceheadachesThe biggest problem: Data changes in one file could cause inconsistenciesCompromises in data integrityDate 7/22/2019Chapter 218Problem with Spreadsheets: RedundancyIn a spreadsheet, each row is intended to stand on its own. As a result, the same information may be entered several timesE.g. The BoyGirlCompare the BoyGirl spreadsheet to BoyGirl Relational database …
22/07/201910Date 7/22/2019Chapter 2NOTE:Not a good design!19BoyGirl Database: SpreadsheetOnegirl can contact manyboys, so ….. we store redundantdata about Bonnie.Date 7/22/2019Chapter 2A BoyGirl Relational Database20No redundant data about BonnieTwo tables with a One-to-Manyrelationship… linked by a Foreign KeyPrimary keysForeign keysPrimary keys
22/07/201911Date 7/22/2019Chapter 2The Problem of Storing Redundant DataDelete:some but not all instances of dataUpdate:some but not all instances of dataInsert:multiple data entry can introduce inconsistencyAlso – very important! –multiple data entry is expensive21Date 7/22/2019Chapter 222SOLUTION: The DATABASE ApproachCentral repository of shareddataData is managed by a controlling agentStored in a standardized, convenient formRequires a Database Management System (DBMS)
22/07/201912Date 7/22/2019Chapter 223Database Management SystemDBMS manages data resources like an operating system manages hardware resourcesAsoftwaresystemthatisusedtodefine,create,maintainadatabase, and providecontrolled accessto user databasesOrder FilingSystemInvoicingSystemPayrollSystemDBMSCentral databaseContains employee,order, inventory, pricing, and customer dataDate 7/22/2019Chapter 22424Advantages of the Database ApproachProgram‐data independencePlanned data redundancyImproved data consistencyImproved data sharingIncreased application development productivityEnforcement of standardsImproved data qualityImproved data accessibility and responsivenessReduced program maintenanceImproved decision support
22/07/201913Date 7/22/2019Chapter 22525Costs and Risks of the Database ApproachNew, specialized personnelInstallation and management cost and complexityConversion costsNeed for explicit backup and recoveryOrganizational conflictDate 7/22/2019Chapter 226Data modeling and design tools –automated tools used to design databases and application programs

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