waterfall model final ppt
TRANSCRIPT
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WATERFALL MODEL
1. The waterfall model was first defined by
Winston W. Royce in 1970 and has been
widely used for software projects ever since.
2. The waterfall Model illustrates the softwaredevelopment process in a linear sequential
flow. This means that any phase in the
development process begins only if the
previous phase is complete.
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CONTD
3. The waterfall approach does not define the
process to go back to the previous phase to
handle changes in requirement. Therefore,
different projects may follow differentapproaches to handle such situations.
4. In Royce's original waterfall model, the
following phases are followed in order
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Traditional Systems Development
Lifecycle (The Waterfall Model)
Planning
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Traditional Systems Development
Lifecycle (The Waterfall Model)
Planning
Analysis
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Traditional Systems Development
Lifecycle (The Waterfall Model)
Planning
Analysis
Logical
Design
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Traditional Systems Development
Lifecycle (The Waterfall Model)
Planning
Analysis
Logical
Design
Physical
Design
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Traditional Systems Development
Lifecycle (The Waterfall Model)
Planning
Analysis
Logical
Design
Physical
Design
Implementation
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STEPS
1. PLANNING:
It involves a macro level study of the customer
requirements. This phase also involves defining
alternative solutions to the customer
requirements and cost-benefit justification of
these alternatives.
2. ANALYSIS :
It involves carrying out detailed study of the
customer requirements and arriving at the exact
requirements of the proposed system. The phase
involves freezing the requirements before the
design phase begins.
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3.DESIGN:
It involves translating the identifiedrequirements into a logical structure, calleddesign that can be implemented in aprogramming logic.
4. TESTING:
It involves integrating and testing all themodules developed in the previous phase asa complete system.
5. IMPLEMENTATION AND MAINTENANCE:
It involves converting the new systemdesign into operation. This may involveimplementing the software system andtraining the operating staff before the
software system is functional.
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When to use the Waterfall
Model
Requirements are very well known
Product definition is stable
Technology is understood New version of an existing product
Porting an existing product to a new
platform.
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WHY NOT WATERFALL
MODEL?
Requirements are not stable/unchanging
The market changesconstantly.
The technology changes.
The goals of the stakeholders change.
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The design may need to change duringimplementation
Requirements are incomplete and changing.
Too many variables, unknowns, andnovelties.
A complete specification must be as detailedas code itself.
Software is very hard- Discover Magazine,1999: Software characterized as the mostcomplex machine humankind builds.
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The waterfall approach assumes that
requirements are stable and frozen acrossthe project plan.
However, this is usually not true in case oflarge projects where requirements may
evolve across the development process.
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ADVANTAGES
Easy to understand, easy to use
Provides structure to inexperienced staff
Milestones are well understood
Sets requirements stability
Good for management control (plan, staff,
track)
Works well when quality is more importantthan cost or schedule
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DISADVANTAGES
All requirements must be known upfront
Deliverables created for each phase areconsidered frozeninhibits flexibility
Can give a false impression of progress Does not reflect problem-solving nature of
software developmentiterations of phases
Integration is one big bang at the end
Little opportunity for customer to previewthe system (until it may be too late)
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ALTERNATIVE TO
WATERFALL MODEL
JAD (JointApplicationDevelopment)
RAD (RapidApplication
Development)
SPIRAL MODEL
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JOINT APPLICATION
DEVELOPMENT (JAD)
It is a process that accelerates the design ofinformation technology solutions.
JAD uses customer involvement and group
dynamics to accurately depict the user's viewof the business need and to jointly develop asolution.
Before the advent of JAD, requirements wereidentified by interviewing stakeholders
individually. The ineffectiveness of thisinterviewing technique, which focused onindividual input rather than group consensus,led to the development of the JAD approach.
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JAD offers a team oriented approach to the
development of information management
solutions that emphasize a consensusbased problem-solving model.
By incorporating facilitated workshops and
emphasizing a spirit of partnership, JAD
enables system requirements to bedocumented more quickly and accurately
than if a traditional approach were used.
JAD combines technology and businessneeds in a process that is consistent,
repeatable, and effective.
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WHEN TO USE JAD
JAD can be successfully applied to a
wide range of projects, including the
following:(17)
New systems
Enhancements to existing systems
System conversions Purchase of a system
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RAPID APPLICATION
MODEL (RAD) Requirements planning phase (a workshop
utilizing structured discussion of businessproblems)
User description phase automated toolscapture information from users
Construction phase productivity tools,such as code generators, screen generators,
etc. inside a time-box. (Dountil done) Cutover phase -- installation of the system,
user acceptance testing and user training
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RAD STRENGTHS
Reduced cycle time and improved productivity with
fewer people means lower costs
Time-box approach mitigates cost and schedule
risk Customer involved throughout the complete cycle
minimizes risk of not achieving customer
satisfaction and business needs
Focus moves from documentation to code(WYSIWYG).
Uses modeling concepts to capture information
about business, data, and processes.
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RAD WEAKNESSES
Accelerated development process mustgive quick responses to the user
Risk of never achieving closure
Hard to use with legacy systems
Requires a system that can bemodularized
Developers and customers must becommitted to rapid-fire activities in anabbreviated time frame.