Chap 1 - System Life Cycle

8/9/2019 Chap 1 - System Life Cycle

1/38

System Life Cycle

Main Menu 1 of 38

System Life Cycle


2/38

System Life Cycle

Main Menu 2 of 38

Objective

To understand various activities involved

in system life cycle and different lifecycle models


3/38

System Life Cycle

Main Menu 3 of 38

Scope

Activities involved in life cycle model

Different life cycle models

Waterfall Model Prototyping

Object Oriented

Dynamic System Development Model Comparing different models


4/38

System Life Cycle

Main Menu 4 of 38

Activities in System Life Cycle

Preliminary

Investigation

Analysis

Design

Development/

coding

Testing

Implementation

and maintenance

Start

Stop

If new additions are to be

introduced in the system


5/38

System Life Cycle

Main Menu 5 of 38


Preliminary Investigation

Identification of problem

Listing down of possible solutions Feasibility Study

Recommendations

Analysis It is the detailed study of various operations

performed by the system


6/38

System Life Cycle

Main Menu 6 of 38


Design

Structure or design for the proposed system is

finalized.These includes files, databases, inputs,

outputs, and screens.

Development

System is built using design specification

Testing

System is tested for its accuracy


7/38

System Life Cycle

Main Menu 7 of 38


Implementation and Maintenance

Implementation is putting the system on users

site for operation

Possible changes leading to changes during the

implementation are:

change in the policies of organization or

change in users requirements, For this maintenance is required.


8/38

System Life Cycle

Main Menu 8 of 38

Life Cycle Models

Waterfall Model

Prototyping

Object oriented Dynamic System Development Method

(DSDM)


9/38

System Life Cycle

Main Menu 9 of 38

Analysis

Design

System Engg.

Coding

Testing

Maintenance

Waterfall Model


10/38

System Life Cycle

Main Menu 10 of 38

Prototyping

Steps:

Identify the users information and operatingrequirements.

Based upon these, build a working prototype ofthe proposed system.

Let the customer evaluate the prototype. If thereare changes suggested, incorporate them in the

prototype.

Repeat the process unless the system meets fulluser requirements


11/38

System Life Cycle

Main Menu 11 of 38

Requirement

gathering

Quick Design

Engineer Product

Building

Prototype

Refining

Prototype

Customer

evaluation

Start

Stop

Prototype Model

Prototyping


12/38

System Life Cycle

Main Menu 12 of 38

Object Oriented Model

This model uses object oriented techniques

during different system development phases

(e.g. analysis, design, implementation)

Everything is viewed as Objects.

Objects can be any distinguishable thing.

It can be person, place, thing, or someconcept.


13/38

System Life Cycle

Main Menu 13 of 38

Object Oriented Process

The system to be developed is observed and

analyzed and the requirements are defined as

in any other method of system development.

Then the objects in the required system are

identified.

Relationships between objects are identified


14/38

System Life Cycle

Main Menu 14 of 38

Object Oriented Process

The basic steps of system designing using

Object Modeling

System Analysis

System Design

Object Design

Implementation


15/38

System Life Cycle

Main Menu 15 of 38

O O Modeling - System Analysis

Developer interacts with the user of thesystem to find their requirements

Study of the system is also done to understand

the functioning

Analyst prepares a model of the desiredsystem showing its possible objects

This model shows the functionality of thesystem. It doesnt show implementationdetails.


16/38

System Life Cycle

Main Menu 16 of 38

O O Modeling - System Design

Architecture of the desired system is decided

The system is organized as a set of

subsystems interacting with each other The stress lies on the objects comprising the

system


17/38

System Life Cycle

Main Menu 17 of 38

O O Modeling - Object Design

The details of the system analysis and system

design are implemented.

The objects identified in the system designphase are designed.


18/38

System Life Cycle

Main Menu 18 of 38

O O Modeling - Implementation

The class objects and the interrelationships of

these classes are coded using programming

language decided upon.

The databases are made and the complete

system is given a functional shape.

S f C l


19/38

System Life Cycle

Main Menu 19 of 38

Basic Object Models

models used by analyst to analyze and depict

objects in a system:

Object Model Dynamic Model

Functional Model

S Lif C l


20/38

System Life Cycle

Main Menu 20 of 38

Basic Object Models

Object Model

describes the objects in a system and their

interrelationships

Observes all the objects as static

Does not pay any attention to their dynamic

nature.

S Lif C l


21/38

System Life Cycle

Main Menu 21 of 38

Basic Object Models

Dynamic Model

depicts the dynamic aspects of the system

Portrays the changes occurring in the states of various

objects with the events that might occur in the system.

Functional Model basically describes the data transformations of the

system

Describes the flow of data and the changes that occur

to the data throughout the system

S Lif C l


22/38

System Life Cycle

Main Menu 22 of 38

DSDM- Dynamic System Development Model

Dynamic approach towards system

development

It is a Rapid Application Developmentmethod

Uses incremental prototyping.

Is independent of tools As it can be used with both structured analysis

and design approach or object-oriented approach.

S t Lif C l


23/38

System Life Cycle

Main Menu 23 of 38

DSDM

Is particularly useful in situations where

System is to be developed in short time span

requirements cannot be frozen at the start of the

application building.

S t Lif C l


24/38

System Life Cycle

Main Menu 24 of 38

DSDM

DSDM is five phase life cycle

Feasibility

Business Study

Functional Model Iteration

Design and Build Iteration

Implementation

S t Lif C l


25/38

System Life Cycle

Main Menu 25 of 38

DSDM - Feasibility Study

Problem is defined

Technical feasibility of the desired

application is verified Applications suitability for Rapid

Application Development (RAD) approach is

checked

S t Lif C l


26/38

System Life Cycle

Main Menu 26 of 38

DSDM - Business Study

Overall business study of the desired system

is done

The business requirements and informationrequirements out of the system are identified

The basic architectural framework of the

desired system is prepared

System Life Cycle


27/38

System Life Cycle

Main Menu 27 of 38

DSDM-Functional Model Iteration

Prototype for the system is built iteratively

Prototype is improved through

demonstration to the user taking the feedback and

incorporating the changes.

Cycle is repeated generally twice or thriceuntil a part of functional model is agreed upon

System Life Cycle


28/38

System Life Cycle

Main Menu 28 of 38

DSDM-Design and Build Iteration

This phase stresses upon ensuring that theprototypes are satisfactorily and properlyengineered to suit their operational

environment Software components designed during the

Functional modeling are further refined till

they achieve a satisfactory standard. The product of this phase is a tested system

ready for implementation.

System Life Cycle


29/38

System Life Cycle

Main Menu 29 of 38

DSDM - Implementation

Users are trained

The system is actually put into the operational

environment.

System Life Cycle


30/38

System Life Cycle

Main Menu 30 of 38

Agr ee pl an

Functi onal

Model

Iteration

Review Pr ot ot ype

Cr eat e

Func.

Pr ot o.

Identify

func

Prot o

I mple ment

Tr ai n

Users

Review

Busi ness

I mple ment ation

Identify design prot ot ype

Desi gn &

buil d iterati on

Revise

desi gn

prot o

Cr eate design prot ot ype

Agree

pl an

User appr oval &gui deli nes

Feasi bilit y

Busi ness

St udy

DSDM System Life Cycle

System Life Cycle


31/38

System Life Cycle

Main Menu 31 of 38

Comparing different models

Waterfall Model

Limitations

Real projects rarely follow sequential flow.

Iterations are always required.

Requirements may not be clearly defined in thebeginning phase.

Customer would have no idea of the workingprogram until the end.

Product delivery takes much time.

System Life Cycle


32/38

System Life Cycle

Main Menu 32 of 38

Prototyping

Limitations

Because of quick design, there can be

compromise on quality.

Advantages:

Reduces risk of uncertainty

Allows early stoppage of unsuccessful projects.

User interaction and involvement is more.

Less chances of error during system design.

System Life Cycle


33/38

System Life Cycle

Main Menu 33 of 38

DSDM Model

Advantages:

Quality of the product is improved due to

Active user participation throughout the life of the

project

Iterative nature of development

DSDM ensures rapid deliveries

Reduced project costs due to advantagesmentioned above

System Life Cycle


34/38

System Life Cycle

Main Menu 34 of 38

Object Oriented Method Advantages

Easier to produce and understand designs as itclosely represents the problem domain

Allows changes more easily as the objects in the

system are immune to requirement changes

Encourages re-use - new applications can use theexisting modules

Reduced development cost and cycle time.

Is more natural

provides nice structure for thinking andabstracting and leads to modular design.

System Life Cycle


35/38

System Life Cycle

Main Menu 35 of 38

Summary

The systems development life cycle consists

of following 5 phases:

Analysis

Design

Coding

Testing

Maintenance

System Life Cycle


36/38

System Life Cycle

Main Menu 36 of 38

Summary

Various life cycles models are available in the

industry.

Traditional(Waterfall)

Prototype

Object-Oriented

Dynamic systems development method

System Life Cycle


37/38

System Life Cycle

Main Menu 37 of 38

Summary

Waterfall Model is a sequential model where

each stage can only start after the previous

stage has finished.

Prototype is an iterative model where

enhancements are made on the prototype of

the system.

Object Oriented Model uses object oriented

techniques during different stages of

development

System Life Cycle


38/38

System Life Cycle

M i M 38 f 38

Summary

DSDM combines RAD with incremental

model of system development.

Each model has its own limitations and

advantages. These should be taken into

consideration while deciding for a

methodology.

Chap 1 - System Life Cycle

Documents