Spiral model explanation

SPIRALMODEL
Group Members:
Mahmood ulhassan
Hamad ul hassan
Hasham haider
Umar Farooq BHatti

Introduction
 The spiral model, also known as the spiral lifecycle model.
 It is a systems development method (SDM) used in information technology
 This model of development combines the features of the prototyping model
and the systems development life cycle (SDLC).
 This model of development combines the features of the prototyping model
and the waterfall model.

Introduction
 This model was not the first model to discuss iterative development.
 As originally envisioned, the iterations were typically 6 months to 2 years long.
 Each phase starts with a design goal and ends with the client (who may be
internal) reviewing the progress thus far.
 Analysis and engineering efforts are applied at each phase of the project, with
an eye toward the end goal of the project.

History Of Spiral model
• Defined by Barry Boehm in his 1986 article "A Spiral Model of Software
Development and Enhancement“
• In 1988 Boehm published a similar paper to a wider audience
Title Computer table of contents
archive
Volume 21 Issue 5, May
1988
Editor Bruce D. Shriver
Page# 61-72
Publication Date 1988-05-01 (yyyy-mm-dd)
Publisher
IEEE Computer Society
Press Los Alamitos, CA,
USA

WHAT IS SPIRAL MODEL?
 The spiral model is similar to the incremental model, with more emphasis
placed on risk analysis.
 The spiral model has four phases: Planning, Risk Analysis, Engineering
and Evaluation.
 Software project repeatedly passes through these four phases in iterations
(called Spirals).
 The baseline spiral, starting in the planning phase, requirements are
gathered and risk is assessed. Each subsequent spirals builds on the
baseline spiral.

Spiral model is meta model?
 Spiral model is also called as meta-model because in a way it comprises of
other models of SDLC.
 Both waterfall and prototype models are used in it.
 Here we do software development systematically over the loops (adhering
to waterfall approach) and at the same time we make a prototype and show
it to user after completion of various phase (just in case of prototype
model).
 This way we are able to reduce risks as well as follow systematic approach

PHASES OF SPIRAL MODEL
A spiral model has 4 phases described below:
 Planning phase
 Risk analysis phase
 Engineering phase
 Evaluation phase.

PLANING
 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.

RISK ANALYSIS
 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

ENGINEERING WORKS
 Actual development and testing if the software takes place in
this phase
 Code
 Test cases and test results
 Test summary report and defect report.

EVALUATION
 Customers evaluate the software and provide their
feedback and approval
 Features implemented document

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 feedback.
 Where releases are required to be frequent.

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).

Advantages
 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

Disadvantages
 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.

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

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

Examples
o The US military had adopted the spiral model for its Future Combat
Systems program. The FCS project was cancelled after six years (2003–
2009), it had a two year iteration (spiral).
o In 2010 with the collaboration of Microsoft Research ,Bangalore, India and
University of Toronto Canada made a project with spiral model “Exploring
the Feasibility of Video Mail for Illiterate Users”

Video Mail for Illiterate Users

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.

Honorable Teacher
• Inspired and helped By:
» Sir Dr. Nadeem Ahmad Chaudhry

References
o What is spiral model and when to use
o http://www.softwaretestinghelp.com/spiral-model-what-is-sdlc-
spiral-model/
o Advantages and dis advantages
o http://www.technotrice.com/what-is-spiral-model-software-
engineering/
o http://dl.acm.org/citation.cfm?id=45801
o Introduction , history
o http://en.wikipedia.org/wiki/Spiral_model
o http://robincse.blogspot.com/2012/03/boehms-spiral-process-
model.html
o Example
o http://www.dgp.toronto.edu/~ravin/papers
o Video mail system for illiterate users

Spiral model explanation

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