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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
Requirement Analysis
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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Requirement Analysis
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
Requirement Analysis
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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Life Cycle vs Methodology
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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Life Cycle vs Methodology
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