Database Systems Design Simplisio Rwezuva

8/3/2019 Database Systems Design Simplisio Rwezuva

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Database Development

The Database Application

LifecycleA Relational Approach


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Broad Goals of Database

DevelopmentDevelop a common vocabularyDevelop a common vocabulary

Define data meaningDefine data meaning

Ensure data qualityEnsure data quality

Provide efficient implementationProvide efficient implementation


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Overview of the DbDLC


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Database Application Lifecycle

Database Planning Focus on management

activities Activities include:

Work to be done Resources available TORs Surely we can spend a

few minutes beforerushing off to spend ourmoney or writeprograms. Isnt thatextra hesitation theessence of design

Gerald Weinberg


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Database Application Lifecycle

System Definition

Scope

Parameters

Application areas

User groups


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Primary Education

Application Areas

Teaching & LearningTeaching & LearningMaterialsMaterials

FacilitiesFacilities

FinanceFinance

LearnersLearners

TeachersTeachers


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What is requirements analysis?

The process ofdefining your

system. A process of:

Discovery Refinement Modelling Specification


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Goals of Requirements Analysis to determine the data requirements of the

database in terms of primitive objects

to classify and describe the information about

these objects to identify and classify the relationships among

the objects

to determine the types of transactions that will

be executed on the database and theinteractions between the data and thetransactions

to identify rules governing the integrity of thedata


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Principles of Analysis

Understand the problem domain Define the software functions to be

performed Represent behaviour of software Model details of data, information,

controls flows & functional behaviour in alayered manner

Move from functions & information outputstowards processing functions & informationstructures


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Building Blocks of An Information system

Focus on

DATA

System owners

View of Data

System UsersView of Data

Designers View

of Data

System builders

View of Data

Focus on

INTERFACES

System owners

View of interfaces

System usersView of interfaces

System designers

View of interfaces

System builders

View of interfaces

INFORMAT

IONTECH

NOLOGY& A

RCHTECTU

RE

Database Technology. Process Technology. Interface Technology

Focus on

PEOPLE

Stakeholders

System

Owners

SystemUsers

System

Designers

System

Builders

Vendors and

Consultants

Focus on

PROCESSES

System owners

View of

processes

System users

View of

processes

System builders

View of

processes

System designers

View of processes


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Building Blocks of An Information system

Focus on

DATA

Business

Knowledge

DataRequirements

Database Models

Database

Programs

DatabaseManagement System

Focus on

PEOPLE

Stakeholders

System

Owners

SystemUsers

System

Designers

System

Builders

Vendors and

Consultants

Focus on

INTERFACES

Focus on

PROCESSES


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Requirements Discovery

Methods Collecting facts from existing

Documentation

Research and site visits Questionnaires

Interviews

Discovery prototyping

Joint Requirements Planning


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Database design

The process of creating a design for a

database that will support the enterprisesoperations and objectives


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Database Design Objectives: Develop detailed technical

specifications for hardware, software, data, peopleand procedures--How the system will be built

End Result: Make orBuy? Detailedfile/database design, program specs, interfacedesign, sizing and response time specs

Methods: CASE tools, End User Computing Skills/Talents Required: Technical

How to Avoid Risk: Careful check vs.functional requirements, management review


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Database designgoalsSatisfy the users content requirements

Ensure the consistency and integrity of

dataProvide a natural easy to understand

structuring of information

Satisfy the user performancerequirements


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Database Design Framework Determine the information requirements

Analyse the real-world objects that you

want to model in the database Determine primary key attributes

Develop a set of rules that govern how eachtable is accessed, populated and updated

Identify relationship between the entities

Plan database security


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Goals for Collecting and Analysing

Data. Identify major functions and activities of

your organisation

Identify the objects of those functions andactivities

Identify the characteristics of those objects

Identify certain relationships between theobjects


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Students and courses


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Identifying entities

Students

Courses

Instructors

StudentCourses

Advisors


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Identifying attributes

What information on each entity should we know?

Students(student_id, Fname, lname, phone, advisor_id)

Advisors(Advisor_id, Advisorname, Advisorphone)

Instructors(instructor_id, Instructorname, Instructorphone)

StudentCourses(Student_id, Course_id)

Courses(Course_id, Coursedescription instructor_id)


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DBMS Selection

The selection of an appropriate DBMS to

support the database application


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Factors to consider

Performance

Ease of restructuring

Integrity constraints

Security


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Development AlternativesDevelopment Alternatives

DifficultiesDifficulties

Operational system is produced lateOperational system is produced late

Rush to begin implementationRush to begin implementation

Requirements are difficult to captureRequirements are difficult to capture

Alternative methodologiesAlternative methodologies

Spiral approachesSpiral approaches

Rapid application developmentRapid application development

Prototypes may reduce riskPrototypes may reduce risk


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Prototyping building an experimental system (prototype: a

preliminary model) rapidly and inexpensively for

end users to evaluate

Using the prototype, end users can better

determine information requirements.

planned iterative process of systems development

less formal requirements determined dynamically as the prototype

is constructed


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Prototyping

DetermineNeeds

BuildPrototype

EvaluatePrototype

AcceptableNo

Yes


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Prototypingcontinued

advantages

useful when there is uncertainty about requirements or

design solutions (decision-oriented solutions)

valuable for the design of the end-user interface

encouraging intense end-user involvement

disadvantages

only suitable for smaller applications

tending to skip essential steps in systems development

hasty construction

poor documentation


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Implementation

Objectives: Implement system, fully-functional,deliverables in priority order, with effective training and

conversion

End Result: Accurately functioning system, properlytrained users

Methods: CASE tools, EUC

Skills/Talents Required: Technical, communication How to Avoid Risk: Communication! Planning!

Change management! Status reviews and walk-throughs!


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Stages of Implementation Hardware/Software Acquisition if needed

Programming

Testing (program, subsystem, system tests) Training (lead users, train the trainer)

Conversion (in order of increasing complexityand risk)

Parallel (old and new systems) Pilot (small scale, small scope)

Phased (most critical functions first)

Direct Cutover (with manual parallel operations)


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Database Maintenance

Objectives: Fix bugs (incorrect program specs orcode) in software, add enhanced functions, cycle back

through SDLC phases as needed for small-scale projects

End Result: Fully Functional Robust System

Methods: As needed for phases above; audit thesystem

How to Avoid Risk: Watch changing businessrequirements, set priorities.

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Database Systems Design Simplisio Rwezuva

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