IST 210 Database Design Process

IST 210Todd S. Bacastow

January 2005

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IST 210 Key pointsDatabase design must reflect the information system of which the database is a partInformation systems undergo evaluation and revision within a framework known as the Systems Development Life Cycle (SDLC)

Databases also undergo evaluation and revision within a framework known as the Database Life Cycle (DBLC)There are two general design strategies exist:

top-down vs. bottom-up designcentralized vs. decentralized design

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IST 210 The Information System

Database Carefully designed and constructed repository of facts Part of an information system

Information SystemProvides data collection, storage, and retrievalFacilitates data transformationIncludes people, hardware, and software

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IST 210 The Information System (Con’t.)System Analysis

Establishes need and extent of an information systemRefer to Recommended Requirements Gathering Practices

We are NOT DOING A SYSTEM REQ’T ANALYSIS!!

Systems developmentProcess of creating information system

Database developmentProcess of database design and implementation

Creation of database modelsImplementation

Creating storage structureLoading data into databaseProviding for data management

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IST 210 Systems Development Life Cycle

System Analysis

Database Lifecycle (DBLC)

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IST 210 Database Lifecycle (DBLC)

Phase 2

Phase 1

Phase 3

Phase 4

Phase 5

Phase 6

DatabaseOrganization

(IST 210)

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IST 210 Phase 1: Database Initial Study

Phase 2

Phase 1

Phase 3

Phase 4

Phase 5

Phase 6

PurposesAnalyze company situation

Operating environmentOrganizational structure

Define problems and constraintsDefine objectivesDefine scope and boundaries

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IST 210 Initial Study Activities

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IST 210 Phase 2: Database Design

Most Critical DBLC phaseMakes sure final product meets requirementsFocus on data requirementsSubphases

I. Create conceptual designII. DBMS software selectionIII. Create logical designIV. Create physical design

Phase 2

Phase 1

Phase 3

Phase 4

Phase 5

Phase 6

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IST 210 Two Views of Data

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IST 210 I. Conceptual Design

Data modeling creates abstract data structure to represent real-world itemsHigh level of abstractionFour steps

Data analysis and requirements*Entity relationship modeling and normalization**Data model verification*

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IST 210 Data analysis and RequirementsFocus on:

Information needsInformation usersInformation sources

Data sourcesDeveloping and gathering end-user data viewsDirect observation of current systemInterfacing with systems design group

Business rules

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IST 210

Entity Relationship Modeling and Normalization

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IST 210 E-R Modeling is Iterative

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IST 210 Concept Design: Tools and Sources

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IST 210 Data Model Verification

E-R model is verified against proposed system processes

End user views and required transactionsAccess paths, security, concurrency controlBusiness-imposed data requirements and constraints

Reveals additional entity and attribute details

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IST 210 E-R Model Verification Process

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IST 210 Iterative Process of Verification

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IST 210 II. DBMS Software Selection

DBMS software selection is critical Advantages and disadvantages need studyFactors affecting purchasing decision

CostDBMS features and toolsUnderlying modelPortabilityDBMS hardware requirements

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IST 210 III. Logical DesignTranslates conceptual design into internal model Maps objects in model to specific DBMS constructsDesign components

TablesIndexes ViewsTransactionsAccess authoritiesOthers

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IST 210 IV. Physical Design

Selection of data storage and access characteristics

Very technicalMore important in older hierarchical and network models

Becomes more complex for distributed systemsDesigners favor software that hides physical details

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IST 210 Phase 3: Implementation and Loading

Creation of special storage-related constructsto house end-user tablesData loaded into tablesOther issues

PerformanceSecurityBackup and recoveryIntegrityCompany standardsConcurrency controls

Phase 2

Phase 1

Phase 3

Phase 4

Phase 5

Phase 6

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IST 210 Phase 4: Testing and EvaluationDatabase is tested and fine-tuned for performance, integrity, concurrent access, and security constraintsDone in parallel with application programmingActions taken if tests fail

Fine-tuning based on reference manualsModification of physical designModification of logical designUpgrade or change DBMS software or hardware

Phase 2

Phase 1

Phase 3

Phase 4

Phase 5

Phase 6

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IST 210 Phase 5: Operation

Phase 2

Phase 1

Phase 3

Phase 4

Phase 5

Phase 6

Database considered operationalStarts process of system evaluationUnforeseen problems may surfaceDemand for change is constant

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IST 210 Phase 6: Maintenance and Evaluation

Preventative maintenanceCorrective maintenance Adaptive maintenanceAssignment of access permissions Generation of database access statistics to monitor performancePeriodic security audits based on system-generated statisticsPeriodic system usage-summaries

Phase 2

Phase 1

Phase 3

Phase 4

Phase 5

Phase 6

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IST 210 DB Design Strategy Notes

Top-down1) Identify data sets2) Define data elements

Bottom-up1) Identify data elements2) Group them into data sets

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IST 210 Top-Down vs. Bottom-Up

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IST 210 Centralized vs. Decentralized Design

Centralized designTypical of simple databasesConducted by single person or small team

Decentralized designLarger numbers of entities and complex relationsSpread across multiple sitesDeveloped by teams

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IST 210 Decentralized Design

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IST 210 SummaryDatabase design must reflect the information system of which the database is a partInformation systems undergo evaluation and revision within a framework known as the Systems Development Life Cycle (SDLC)

Databases also undergo evaluation and revision within a framework known as the Database Life Cycle (DBLC)There are two general design strategies exist:

top-down vs. bottom-up designcentralized vs. decentralized design