Waterfall Model Final Ppt

8/11/2019 Waterfall Model Final Ppt

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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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Planning

Analysis


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Planning

Analysis

Logical

Design


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Planning

Analysis

Logical

Design

Physical

Design


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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.

Documents

Waterfall Model Final Ppt