Database Management System - Chapter 2: Introduction to Database Management (tt)

Chapter 2Introduction to Database DevelopmentOutline Context for database developmentGoals of database developmentPhases of database developmentCASE toolsInformation SystemTraditional Life CycleDevelopment AlternativesDifficultiesOperational system is produced lateRush to begin implementationRequirements are difficult to captureAlternative methodologiesSpiral approachesRapid application developmentPrototypes may reduce riskGraphical ModelsExplicit or implicitData modelProcess modelEnvironment interaction modelEmphasize data modelBroad Goals of Database DevelopmentDevelop a common vocabularyDefine data meaningEnsure data qualityProvide efficient implementationDevelop a Common VocabularyDiverse groups of usersDifficult to obtain acceptance of a common vocabularyCompromise to find least objectionable solutionUnify organization by establishing a common vocabularyDefine Meaning of DataBusiness rules support organizational policiesRestrictiveness of business rulesToo restrictive: reject valid business interactionsToo loose: allow erroneous business interactionsExceptions allow flexibilityData QualityPoor data quality leads to poor decision makingDifficult customer communicationInventory shortagesCost-benefit tradeoff to achieve desired level of data qualityLong-term effects of poor data qualityData Quality MeasuresCompletenessLack of ambiguityTimelinessCorrectnessConsistencyReliabilityEfficient ImplementationSupersedes other goalsOptimization problemMaximize performanceSubject to constraints of data quality, data meaning, and resource usageDifficult problem: Number of choicesRelationships among choicesDBMS specificDatabase Development PhasesConceptual Data ModelingLogical Database DesignDistributed Database DesignPhysical Database DesignERDTablesDistribution SchemaInternal Schema, Populated DBData requirementsConceptual Data ModelingInformation content of the databaseEntity relationship diagram (ERD) showing entity types and relationshipsHistorically, DBMSs did not support many constraints.Diverse formats for database requirementsLogical Database DesignRefine conceptual designConvert ERD to table designAnalyze design for excessive redundancies Normalization: tool to reason about redundanciesAdd constraints to enforce business rulesDistributed Database DesignLocation of data and processingPerformance orientation, not information content orientationAllocate subsets of database to different sites Replicate subsets of database to improve availabilityPhysical Database DesignPerformed at each independent database siteMinimize response time without consuming excessive resourcesTradeoffs: retrieval versus updateFlexible designs versus specialized designs Decisions: indexes, data placementSplitting Conceptual DesignCross Checking RequirementsDesign SkillsSoftQualitativeDegree of subjectivityPeople-orientedHardQuantitativeObjectiveIntensive data analysisDesign Skills in PhasesFeatures of CASE ToolsDiagrammingDocumentationAnalysisPrototypingClassification of CASE ToolsFront-end vs. Back-endFront-end emphasize data modeling and logical analysisBack-end emphasize code generation and physical designDBMS dependent vs. DBMS independentCommercial CASE ToolsPowerDesigner 10Oracle Designer 10gVisual Studio .Net Enterprise ArchitectERWin Data ModelerER/StudioVisible AnalystER AssistantCASE tool distributed with the textbookCustomized for this textbook: supports the ERD notation used in Chapters 5 and 6Drawing toolDiagram checkingEasy to use and powerful toolVisio ProfessionalEntry level version of Visual Studio .Net Enterprise ArchitectDrawing toolsStencils for database diagramsGlue feature to retain connectionsData dictionary supportAnalysis toolsDiagram layoutReverse engineeringSummaryBackground for Chapters 5 to 8 Relationship to information systems developmentBroad goalsDevelopment phasesCASE tool features