system analys & DLC

8/7/2019 system analys & DLC

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Bachelor of Information Technology

External Degree Programme

Systems Analysis and Design

University of Colombo School of Computing

Ref_1 : System Analysis and Design Methods By Whitten, Bentley, Dittman ISBN 0-07-044539-7 (5th Edition)Ref_2 : System Analysis and Design By Igor Hawryszkiewycz (4th Edition) ISBN 81-203-1670-3

Ref_3 : http://www.mhhe.com/whittenRef_3 : Practical SSADM Version 4 A Complete Tutorial Guide By Philip L Weaver ISBN 0-273-60095-8


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System

DevelopmentLife Cycle


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System Development Life Cycle

(SDLC)

Problem Definition

RequirementAnalysisMaintenance

System Design

System

Development

System Testing


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Feasibility Study

Requirement Analysis

Logical Design

Physical Design

Coding &Testing

Transition

Post implementation

Review

System

Analysis

System

Design

System

Development

System

Operation &

Maintenance


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Advantages of life cycle

Guides the systems

development

Provides a moreefficient / effectivesystem

Facilitate project

review

Computer-based

support

Improve management

and controlImprove

communications


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Waterfall Cycle

Problem Definition


System Design

Implementation

System Testing

Maintenance


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Definition the Problem

Project

limits

Provides a broad statement of userrequirements in users terms, or whatthe users expect the system to do

project bounds are set during thisphase. Defines what part of the

system can be changed by the project

and what parts are to remain same.

Specify the resources to be made

available for the project (resource

limits). Project goals, project boundsand resource limits are some times

called projects terms of reference.

They are set by the organizationsmanagement.

Projectgoals

Project

bound


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how the currentsystem works and

what it does

Producing a detailed model in subject

terms of what the new system will do and

how it will work.

Producing a high-level

description of the system


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System Design

Produces a designspecification for thenew system

Analysts

Design


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System Design

Things to be done:

Select equipment Specify new programs

or changes to existingprograms

Specify new databaseor changes to existingdatabase

produce detailedprocedures

Design


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System Development

Analysts System

Individual system components are built and

tested

Data and tools are used to build the system

User interfaces are developed and tried by

users

Database is initialized with data


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System testing

Test and evaluate results, and

the system ready to bedelivered to the user/client.


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MaintenanceEliminate errors in the system

during its working life.Fixing any bugs and problem found

by users

Tune the system to any variations in

its working environment


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Problems with waterfall cycle

It has rigid design and inflexible procedure

It is top-down procedure

One phase must be completed before thenext phase starts, and

No phase can be repeated.


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Criticisms fall into the following

categories:

Real projects rarely follow the sequential

flow that the model proposes.At the beginning of most projects there is

often a great deal of uncertainty aboutrequirements and goals, and it is therefore

difficult for customers to identify these

criteria on a detailed level. The model doesnot accommodate this natural uncertainty

very well.


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Modified waterfall model

Problem Definition


System Design

Implementation

System Testing

Maintenance


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Spiral model has four phases

Requirement analysis Design prototype

Develop and integrate

Acceptances and testing


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Life Cycle vs Methodology

The software development processconsists of several well-defined steps.

When following a design methodology,a designer can select appropriatemodeling method related to each step


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Conversion

Obsolescence

Lifetimeof a

System

LIFE CYCLE STAGE

System

Development

using

System Development

Methodology

LIFE CYCLE STAGE

System Operationand Support

using

Information

Technology

A system life cycle

divides the life of aninformation system

into two majorstages, systems

development and

systems operation

and support.


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A system development methodology is

a very formal and precise systemdevelopment process that defines

a set of activities,

methods,

best practices,

deliverables, and automated tools


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A System Development methodology

(Process) has some general principles.

P1: Get the owner and User Involved

SystemDevelopmentInvolved


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P2: Use a problem-solving approach.

# Study and understand the problem and itscontext

# Define the requirement of a suitable

solution.

# Identify candidate solutions and select the

best solution.

# Design and/or implement the solution.

# Observe and evaluate the solutionsimpact, and refine

the solution accordingly.


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P3:Establish phases and activities.

# Preliminary investigation

# Problem analysis

# Requirement analysis

# Decision analysis

# Design

# Construction

# Implementation


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P4: Establish standards.

# Documentation # Quality

# Automated tools #Information Technology


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P5:Justify systems as capital investments.

# Cost-effectiveness

IS

cost

# Risk management


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P6:Dont be afraid to cancel or revise

scope.

# Cancel the project if it is no

longer feasible

# If project scope is to be

increased, reevaluate and adjust

the cost and schedule

# If the project budget and

schedule are frozen and notsufficient to cover all project

objectives, reduce the scope.

Cancel


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P8: Design systems for growth and change.

# Correcting simple mistakes

# To redesigning the system to

accommodate changing technology

# To making modification to support

changing user requirements.


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Development Process

Methodology Modeling Methods or Techniques

Tools

Major

Components


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Methodology

Provides the framework Has a predefined set of steps

Ensures that systems are built in the mosteffective way

e.g. SSADM, RUP


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Methodology

Uses tools and modeling methods

Tools

Methods

Most Effective

Way of

Building


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Modeling Methods

A set of techniques used to implement aMethodology

Data Flow Diagrams

Entity Relationship Diagrams

Structure Charts etc.

Different Views

of the System


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System Development Methodologies

Supported by Modeling Methods or

Techniques

Techniques used to implement the Methodology.

Provides the descriptions of the business system

requirements from various view points.


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Tools

Software systems Assists analysts and designer to build

information systems.

e.g. Easy Case, Rational Rose


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System Development Methodologies.

Supported by Tools.

They will not replace Systems Analysts.


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MethodologyEg .Rational Unified Process

uses

uses

Modeling Methods or

Techniques

Class Diagram,

Use Case Diagrams etc.

Tools

Rational Rose,

Rational Suit

system analys & DLC

Documents

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