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Transcript of 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
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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
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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
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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?
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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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Prof. Nivedita Roy, IBS-Gurgaon 12
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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Prof. Nivedita Roy, IBS-Gurgaon 13
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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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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Prof. Nivedita Roy, IBS-Gurgaon 16
Other Data Analysis Tools
Grid chart
System flowchart
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Contd.
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Decision Tree
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Prof. Nivedita Roy, IBS-Gurgaon 18
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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Prof. Nivedita Roy, IBS-Gurgaon 20
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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Prof. Nivedita Roy, IBS-Gurgaon 21
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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Prof. Nivedita Roy, IBS-Gurgaon 22
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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Prof. Nivedita Roy, IBS-Gurgaon 23
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
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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
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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
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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
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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