The Spiral Model is a software development process that combines elements of prototyping and the waterfall model. It emphasizes risk analysis at each phase of development, allowing for iterative refinement. The key aspects are: 1) It consists of four phases - planning, risk analysis, engineering, and evaluation - that are repeated for each iteration. 2) Risk management is explicitly included to help control the software development process. 3) It extends products from earlier iterations through continuous refinement of requirements, design, and implementation.

1. Spiral Model
Submitted To :
Inam Ul-Haq
Lecturer in Computer Science
University of Education, Okara Campus
Submitted By:
Muhammad Yameen Shakir 3001
Faisal Islam Mujahid 3003
Course Name : Software Engineering
University of Education, Okara Campus
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2. Table of Contents
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Introduction
History of Spiral Model
Spiral Model Phases
Importance & Scope
Advantages and Disadvantages of Spiral model
Comparison b/w SM and WM
Evaluation
Conclusion
References
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3. University of Education, Okara Campus
Spiral Model
The Spiral model is a software development process
combining elements of both design and prototyping-in-stages, in an effort to
combine advantages of top-down and bottom-up concepts.
The spiral model also explicitly includes risk
management within software development. Identifying major risks, both
technical and managerial, and determining how to lessen the risk helps keep
the software development process under control.
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4. Spiral Model
The spiral model is based on continuous
refinement of key products for requirements definition and analysis,
system and software design, and implementation (the code).
At each iteration around the cycle, the
products are extensions of an earlier product.This model uses many
of the same phases as the waterfall model, in essentially the same
order, separated by planning, risk assessment, and the building of
prototypes and simulations.
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5. History
 The spiral model was defined by Barry Boehm in his 1988 article.
 This model was not the first model to discuss iterative development, but it
was the first model to explain why the iteration matters.
 In 1988 Boehm published a similar paper to a wider audience
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6. Spiral Model Phases
• A spiral model has 4 phases described below:
 Planning phase
 Risk analysis phase
 Engineering phase
 Evaluation phase.
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7. Spiral Model diagram
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8. Planning Phase
 Requirements are studied and gathered.
 Feasibility study
 Reviews and walkthroughs to streamline the requirements
 Requirements understanding document
 Finalized list of requirements.
 The project is reviewed and a decision made whether
to continue with a further loop of the spiral.
 If it is decided to continue, plans are drawn up for the next phase of
the project.
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9. Risk analysis phase
Requirements are studied and brain storming sessions are done to
identify the potential risks
Once the risks are identified , risk mitigation strategy is planned and
finalized
Document which highlights all the risks and its mitigation plans
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10. Engineering Phase
Actual development and testing if the software takes place in this
phase
Code
Test cases and test results
Test summary report and defect report.
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11. Evaluation phase.
 Customers evaluate the software and provide their feedback and
approval
 Features implemented document
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12. When to use spiral model ?
 When the project is large.
 Where the software needs continuous risk evaluation.
 Requirements are a bit complicated and require continuous
clarification.
 Software requires significant changes.
 Where enough time frame is their to get end user feed12back.
 Where releases are required to be frequent.
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13. When to use spiral model ?
 When costs and risk evaluation is important.
 For medium to high-risk projects.
 Long-term project commitment unwise because of potential changes to
economic priorities.
 New product line.
 Users are unsure of their needs.
 Requirements are complex.
 Significant changes are expected (research and exploration).
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14. Advantages of SM
 Development is fast
 Larger projects / software are created and handled in a strategic way
 Risk evaluation is proper.
 Control towards all the phases of development.
 More and more features are added in a systematic way.
 Software is produced early.
 Has room for customer feedback and the changes are implemented faster.
 Risk reduction mechanisms are in place.
 Supports iteration and reflects real-world practices –Systematic approach
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15. Disadvantages of SM
 Risk analysis is important phase so requires expert people.
 Is not beneficial for smaller projects.
 Spiral may go infinitely.
 Documentation is more as it has intermediate phases.
 Complex, relatively difficult to follow strictly.
 Applicable only to large systems
 It is costly for smaller projects.
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16. Comparison
Spiral Model
 Risk factors are considered.
 The requirements are not
freeze.
 works in loop.
 costly as Risk factor is
covered.
 Better communication
between developer and
customer.
Waterfall model
 Risk factors are not
considered.
 The requirements are freeze.
 Is linear sequential model.
 Not much costly.
 Communication level is not
high

17. Comparison
Spiral Model
 Number of phases is not
fixed.
 Used when requirement is
not clear and needs
conformation
 customer interaction
continuous to move
together.
 Risk factor is considered
prototype model
 Number of phases is fixed.
 Requirement are clear but
complex.
 Customer interaction needs till
the prototype is app.
 Risk factor are not considered

18. Summary
• The Spiral Development ( or Lifecycle) Model is a systems
development method used in information technology.
• It combines the features of the prototyping model and the waterfall
model.
• It is favored for large, expensive, and complicated models.
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19. Conclusion
 Each spiral can be termed as a loop and each loop is a separate
development process in a spiral model.
 The four activities (Planning, Risk analysis, engineering and
evaluation) form the intermediary phases of a spiral model and
is repeated again for each loop.
 This model is very good to use for larger projects where you
can develop and deliver smaller prototypes and can enhance it
to make the larger software.
 The implementation of this model requires experienced
resources as risk analysis is a very integral part of this model
and risk analysis requires expertise and as a result this model
becomes costly.

20. References
http://www.tutorialspoint.com/sdlc/sdlc_spiral_model.htm
Advantages and disadvantages
o http://www.technotrice.com/what-is-spiral-model-software-engineering/
Introduction , history
o http://en.wikipedia.org/wiki/Spiral_model
o http://robincse.blogspot.com
What is spiral model and when to use
o http://www.softwaretestinghelp.com/spiral-model-what-is-sdlc-spiral-
model/
o boehms-spiral-process-model.html
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21. Best of Luck for Future
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