5. is development concepts

7/31/2019 5. Is Development Concepts

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Prof. Nivedita Roy, IBS-Gurgaon 1


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Using the Systems Approach in Problem SolvingThe systems approach to problem solving involves

the following steps:

Define the problem

Gather data describing the problem

Identify alternative solutions

Evaluate the alternatives

Select and implement the best alternative Follow up to determine if the solution is working

Prof. Nivedita Roy, IBS-Gurgaon2


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Obtaining Information System

Organizations can obtain new information systems in oneof the following ways:

Build the IS themselves

Buy a prepackaged system from a softwaredevelopment company or consulting firm

Ask an outside organization or consultant custom builda system to an organizations specification



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Systems Development: An Overview

Activities involved in producing an IS solution to anorganizational problem or opportunity are calledsystems development

This is a structured kind of problem solving with

distinct activities moving from one step to the other

The process of designing, building and maintaininginformation systems is known as systems analysis anddesign

The term systems development life cycle (SDLC) isused to describe the life of an information system rightfrom its conception till its retirement



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Contd.

Large complex problems are decomposed into smalleronce to arrive at better solutions

These smaller problems are solved through small

computer programs

The final system is built by combining these smaller

computer program

Systems development process starts when management

realize that a particular business system needsimprovement



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Approaches to IS Development

Traditional Systems Development Approach (SDLC)

Prototyping

Rapid Application Development

Object Oriented Approach



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Prof. Nivedita Roy, IBS-Gurgaon7

PreliminaryInvestigation

ProblemDefinition

AnalysisGather dataAnalyze dataDeveloprequirements

DesignPreliminarydesignDetail design

DevelopmentSchedulingProgrammingTesting

ImplementationTrainingConversionEvaluation

Maintenance

Ongoing Activities

Project Management

Feasibility Assessment

Documentation

Information Gathering.

Systems Development Life Cycle


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Alternate Representation of SDLC

Six-phase problem-solving procedure for examining

and improving an information system



Preliminary Investigation

A brief study of the problem to determine whether the

project should be pursued

Also called the feasibility study or system survey

Defines the problem

The nature of the problem

The scope (boundaries) of the problem

Also involves working with the users



Analysis

Understand the existing system

Two tasks are involved

Data gathering

Data analysis

This also involves feasibility studyTechnical : Assess hardware, software, technical

resources

Economic: Will benefits outweigh costs?

Operational : Is solution desirable within existing

conditions?



Data Gathering

A number of techniques can be used

Written documents

Interviews with users and managers

Structured interviewincludes only questionsthat have been written out in advance

Unstructured interviewinterviewer has ageneral goal but few, if any questions prepared

Questionnaires

Observation

Sampling


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Data Analysis

Typical tools for data analysisData flow diagram

Decision table/Tree

Checklist

Top-down analysis method

Grid chart

Structured English

Automated design toolsCASE

Create system requirements

Report to management


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Data Flow Diagram

A map that graphically shows the flow of datathrough a system

Used to diagram existing procedures and dataflows


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15/46Prof. Nivedita Roy, IBS-Gurgaon15

1.0

Receive andtransform

Customer FoodOrder

2.0

UpdateInventory

file

3.0

UpdateGoods

Sold file

4.0

ProduceManagement

Reports

CUSTOMER KITCHEN

RESTAURANT

MANAGER

Food Order

Customer Order

Receipt

ManagementReports

Goods Sold

File

D1D2 Inventory

File

Goods

Sold

Inventory

Data

GoodsSoldData

InventoryData

Daily Goods SoldAmount

Daily Inventory Depletion Amounts


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Other Data Analysis Tools

Grid chart

System flowchart


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Contd.


Decision Tree


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Decision Tables

Show the table of

logical decisions that

must be made

Useful in cases thatinvolve a series of

interrelated

decisions

Help to ensure no

alternatives are

overlooked


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Structured EnglishCommon Statements Example

Action Statement Profits = Revenues - ExpensesGenerate Inventory - Report

Add Product record to Product Data Store

If Statement IF Customer Not in Customer Data Store

THEN Add Customer record to Customer Data StoreELSE Add Current-Sale to Customers Total-SalesUpdate Customer record in Customer Data Store

For Statement FOR all Customers in Customer Data StoreGenerate a new line in the Customer-Report

Add Customers Total-Sales to Report-Total

Case Statement CASEIf Income < 10,000: Marginal-tax-rate = 10%If Income < 20,000: Marginal-tax-rate = 20%If Income < 30,000: Marginal-tax-rate = 31%If Income < 40,000: Marginal-tax-rate = 35%ELSE Marginal-tax-rate = 38%

ENDCASE


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Individuals Involved in Systems Analysis

Systems analystperforms analysis and design

May perform some programming as well

Client the person or organization contracting tohave the work done

User the people who will have contact with the

system


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Systems Design The new system is actually planned

Divided into two sub phases Preliminary design

Several key decisions must be made

Build a prototype Detail design specifications

Output requirements

Input requirements

Files and databases

System processing

System controls and backups


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Build or Buy?

Custom Software

Developed by user

Developed at user

request by outside

vendor

Packaged Software

Horizontal

Many org types

Vertical

Industry specific


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Systems Development

Schedule and monitor the two principal activities

Programming

Testing

There are several project scheduling toolsavailable


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Programming

Specifications prepared in the design phase are then

translated into the software program codes in thisstage

Prepare program design specifications

Use logic flowcharts and pseudocode to facilitate codedevelopment

Following two approaches are followed for this:

- Software programs are written within the

organization itself

- Application software packages are purchased for

this



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Testing

This stage is very important to ensure that the systemdeveloped is capable of producing the right results

under known circumstances

This involves the following aspects:

Unit testingverifies that individual program units work

Perform testing with test data

System testingdetermines whether all program units worktogether as planned

Volume testinguses real data in large amounts Determines whether the system can handle a large volume of data



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Implementation

Steps involved in starting the new system

Training

Equipment conversion

File conversion

System conversion

Auditing

Evaluation

Maintenance


Contd


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Contd.

Training:

Teach users how to use the system The system will do no better than the people using it

Develop users manual to aid users who are not familiar

with the system

Hands-on training is best

Equipment Conversion

Delivery schedules must be coordinated

Terminals or personal computers must be networked Devices on the system must be compatible


Contd


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Contd.

File conversion:

If existing files are manual, they must be keyed in or scanned into the

system If existing files are computer-based, programs must be written to

convert the files into the format needed for the new system

System Conversion:

Four approaches Direct conversionthe user simply stops using the old system and

starts using the new one

Phased conversionthe system is implemented one part at a time

Pilot conversionthe entire system is used by a designated set ofusers

Parallel conversionthe old and new systems are both used until users

are satisfied the new system works



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Maintenance

Systems maintenance is very important and is an ongoing

activity

Two parts:

Systems Audit

Systems to trace data in the system back to a sourcedocument

Very helpful in tracing security violations

Periodic evaluation

Determines how well the system is meeting the

original requirements, benefits, and budgets


C td


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Contd.

The system maintenance process is parallel to theprocess of initial development of the IS

During this phase the largest part of the systemsdevelopment effort occurs

Maintenance activity could be of one of the following

types:- Corrective maintenance

- Adaptive maintenance

- Perfective maintenance

- Preventive maintenance



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Prototyping : An Overview

Prototype refers to a working model of an informationsystem application

But it does not contain all the features or perform allthe necessary functions of the final system

However, it includes sufficient elements to enableindividuals to determine what they like or dont likeand also to identify features to be added or changed

It is a process of building experimental system quicklyand inexpensively for demonstration and evaluation



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Characteristics of Prototypes The prototype is a live, working application

The purpose is to test the assumptions made by

analysts and the users about required system features

These are created quickly

They evolve through an iterative process

Prototypes are relatively inexpensive to build



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Uses of Prototyping

Prototyping has the following two primary uses:

Acts as an effective device for clarifying user

requirements It is used for verifying the feasibility of a system

design



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Steps in Prototype Method

Identify known requirements

Develop working model

Use prototype

Review prototype

Repeat as needed



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Alternative Uses of Prototype

Abandon application

Implement prototype

Redevelop prototype

Begin new prototype


R id A li i D l


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Rapid Application Development

(RAD Approach)

Process for developing systems in short time period

Uses prototyping, fourth-generation tools, and close

teamwork to move progressively closer to correct

design

A prototype is a small-scale representative or working

model of the proposed system

Iterative (or spiral) process of developing demo or

working models Refined based upon user review



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Rapid Application Development (RAD)

Develop system rapidly:

Prototyping

4th GENERATION TOOLS

Close teamwork among users & specialists



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Contd.

Helps users definerequirements

Encourages active userparticipation

Errors and omissionstend to be detectedearlier

Builds enthusiasm andacceptance for system

Prototype may meet

requirements but not be

best design

Systems specifications

often not adequately

spelled out

Advantages Disadvantages



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The Object Oriented Approach

OO approach This approach views an information system as a collection of

interacting objects that work together to accomplish tasks

Object A component in the computer system that can respond to

messages.

OO Design- Defining all of the types of objects necessary to communicate

with people and devices in the system and refining thedefinition of each type of object so it can be implemented witha specific language or environment

OO Programming Writing statements in a programming language to define what

each type of object does, including the messages that objectssend and receive.



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Object - Oriented Software Development

De-emphasizes procedures

Shifts focus from models & data

Toobjects, which combine data & procedures Objects reusable

SYSTEM: classes, objects, relationships

Reduces development time & cost



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Alternative System-building Approaches

Application software packages

End-user development

Outsourcing



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Application Software Packages

Prewritten, pre-coded application software,

commercially available for sale or lease

Geared to common requirements

Customization: modification of software to meetorganizations needs

Must weigh costs / benefits

Request For Proposal (RFP): detailed questions sent

to vendors



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End-user Development

End-users develop information system with little help

from technical specialists using 4th generation tools

STRENGTHS

Improved requirements determination, increased user

involvement & satisfaction, reduced application backlogWEAKNESSES

Relatively inefficient, slow transaction processing, may

carry high cost, large files can degrade performance,

nonprocedural approach may hamper logic & updatingrequirements



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Outsourcing

Contracting:

Computer center operations

Telecommunications networks

Application development

To external vendors



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OutsourcingWhen to outsource????

If firm wont distinguish itself by developing

application If predictability of uninterrupted service not important

If existing system is limited, ineffective, inferior

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