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Chapter 2Chapter 2

The database The database development processdevelopment process

The database The database development processdevelopment process

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ess Information Systems

ArchitectureInformation Systems

Architecture

A conceptual blueprint or plan that expresses

the desired future structure for the

information systems in an organization.

A conceptual blueprint or plan that expresses

the desired future structure for the

information systems in an organization.

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ess Architecture exampleArchitecture example

CIM

EDI

External database

access

Business Operations

Customers& Suppliers

External Events

Data validation

and retention

Integrated data warehouse

Access analysis and presentation

tools

Informationdelivery system

Dialogue

Decision makersCustomers, Suppliers

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ess A more sophisticated example...A more sophisticated example...

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Information Systems ArchitectureInformation Systems Architecture Key components:

• data• processes which manipulate data• network which transports data• people who perform processes and send and receive

data• events and points in time when processes are performed• reasons for events and rules which govern data

processing

Key components:• data• processes which manipulate data• network which transports data• people who perform processes and send and receive

data• events and points in time when processes are performed• reasons for events and rules which govern data

processing

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Information EngineeringInformation Engineering

An Information Systems Architecture is developed by IS planners following a particular methodology

such as Information Engineering.

An Information Systems Architecture is developed by IS planners following a particular methodology

such as Information Engineering.

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Information EngineeringInformation Engineering

Data-oriented methodology

Uses top-down planning in which specific information systems are deduced from a broad understanding of organization’s information needs, rather than relying on specific user information requests

Offers perspective on relationship of information systems to business objectives

Data-oriented methodology

Uses top-down planning in which specific information systems are deduced from a broad understanding of organization’s information needs, rather than relying on specific user information requests

Offers perspective on relationship of information systems to business objectives

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Top-Down vs. Bottom-UpTop-Down vs. Bottom-Up

Top-Down Planning:

A methodology that attempts to gain a broad understanding of the information system needs of the entire organization

Top-Down Planning:

A methodology that attempts to gain a broad understanding of the information system needs of the entire organization

Bottom-Up Planning:

A methodology that identifies and defines IS development projects based upon solving operational business problems or taking advantage of business opportunities

Bottom-Up Planning:

A methodology that identifies and defines IS development projects based upon solving operational business problems or taking advantage of business opportunities

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The big picture...The big picture...Information engineering

Information systems planning– Identify strategic planning factors (goals,

CSFs, problem areas)• IT vision

– Identify corporate planning objectives• Information system architecture

– Develop enterprise modelSystems analysisSystems designimplementation

Information engineeringInformation systems planning

– Identify strategic planning factors (goals, CSFs, problem areas)

• IT vision– Identify corporate planning objectives

• Information system architecture– Develop enterprise model

Systems analysisSystems designimplementation

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Systems Development Life CycleSystems Development Life Cycle

Project Identification & Selection

Project Initiation & Planning

Analysis

Logical Design

Physical Design

Implementation

Maintenance

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Database SDLCDatabase SDLC

Identify Project

Initiate and Plan

Analyze

Logical Design

Physical Design

Implementation

Maintenance

EnterpriseModeling

ConceptualData Modeling

LogicalDB Design

Physical DBDesign/Creation

DBImplementation

DBMaintenance

Database Development Activities

SDLC

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Planning MatrixesPlanning Matrixes

Show interrelationships between objects. Among the possibilities:

• Location-to-Function

• Unit-to-Function

• Information System-to-Data Entity

• Supporting Function-to-Data Entity

• Information System-to-Objective

Show interrelationships between objects. Among the possibilities:

• Location-to-Function

• Unit-to-Function

• Information System-to-Data Entity

• Supporting Function-to-Data Entity

• Information System-to-Objective

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essBusiness Function-to-Data Entity Planning

MatrixBusiness Function-to-Data Entity Planning

Matrix

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MatrixInformation System-to-Objective Planning

Matrix

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Functional DecompositionFunctional Decomposition

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Enterprise Data ModelingEnterprise Data Modeling

The first step in database development, in which the scope and

general contents of organizational

databases are specified.

The first step in database development, in which the scope and

general contents of organizational

databases are specified.

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Enterprise Data Model Enterprise Data Model

A model which includes:

• overall range of organizational databases

• general contents of organizational databases

Built as part of IS planning for the organization and not the design of a particular database

One part of an organization’s overall information systems architecture (ISA)

A model which includes:

• overall range of organizational databases

• general contents of organizational databases

Built as part of IS planning for the organization and not the design of a particular database

One part of an organization’s overall information systems architecture (ISA)

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Determine user requirements

Determine business rules

Build conceptual data model

• outcome is an entity-relationship diagram or similar communicationtool

• population of repository

Conceptual Database Modeling

EnterpriseModeling

ConceptualData Modeling

LogicalDB Design

Physical DBDesign/Creation

DBImplementation

DBMaintenance

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Logical Database DesignLogical Database Design

Select logical database model

• commit to a database alternative

Map Entity-Relationship Diagrams

Normalize data structures

Specify business rules

EnterpriseModeling

ConceptualData Modeling

LogicalDB Design

Physical DBDesign/Creation

DBImplementation

DBMaintenance

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Physical Database DesignPhysical Database Design

Select DBMS

Select storage devices

Determine access methods

Design files and indexes

Determine database distribution

Specify update strategies

EnterpriseModeling

ConceptualData Modeling

LogicalDB Design

Physical DBDesign/Creation

DBImplementation

DBMaintenance

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Database implementationDatabase implementation

Code and test database processing programs

Complete documentation

Install database and convert data

Code and test database processing programs

Complete documentation

Install database and convert data

EnterpriseModeling

ConceptualData Modeling

LogicalDB Design

Physical DBDesign/Creation

DBImplementation

DBMaintenance

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Database MaintenanceDatabase Maintenance

Analyze database and applications to ensure evolving information requirements are being met

Tune database for improved performance

Fix errors

Provide data recovery when needed

Analyze database and applications to ensure evolving information requirements are being met

Tune database for improved performance

Fix errors

Provide data recovery when needed

EnterpriseModeling

ConceptualData Modeling

LogicalDB Design

Physical DBDesign/Creation

DBImplementation

DBMaintenance

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Documentation most formal development methodologies are

documentation based

helps managers monitor progress and quality of project

facilitates communication between team members

includes models

various stages are not complete until documentation is accepted

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Some Keys to Success...

accurate requirements definition

commitment

effective change management

manageable size

champion

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So …

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Three Schema Architecture for Database Development

Three Schema Architecture for Database Development

Conceptual Schema

• Analysis project phase

External Schema

• Analysis and Logical Design phases

• (subset of conceptual schema)

Internal Schema

• Physical Design phase

Conceptual Schema

• Analysis project phase

External Schema

• Analysis and Logical Design phases

• (subset of conceptual schema)

Internal Schema

• Physical Design phase

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ess 3-schema architecture3-schema architecture

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Conceptual SchemaConceptual Schema

Describes the logical structure of the entire database

Independent of a specific DBMS

Avoids details of physical design

Stated in

• ERDs

• metadata

Describes the logical structure of the entire database

Independent of a specific DBMS

Avoids details of physical design

Stated in

• ERDs

• metadata

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External Schema

Also called a user view

Specifications include screen formats, report formats, transaction definitions

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Physical Schema Describes physical structure of entire database

Specifies how data from a conceptual schema are stored in secondary memory

Sometimes called internal schema

Specifications include physical file and data structures, storage organization, and index structures

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ess 3-schema development process3-schema development process

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design methodology which speeds systems delivery through a combination of speedy design iterations, data modeling, user/developer teamwork, and automated development tools.

encompasses a set of techniques that can be used to build complex, strategic, and mission-critical applications in months rather than years

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RADRAD

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requirements planning

• conduct joint requirement planning workshop

design

• conduct JAD workshop

construction

• members of team monitor evolution, system is prototyped

cutover

• installation

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Within the time box...Requirements planning

User design

build and evolve prototype

User review

Evaluate system

time box

cutover

request for change

construction phase

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Barriers to overcome...

poor training/ tools

reluctance to leave old methods behind

mindset that RAD is not adequate for large-scale systems development

speedy delivery does not mean low quality

“creeping functionality”