Analysis of The Spiral Method

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Analysis of
The
Spiral Method
Presentation by Danielle Phelps and Conor Mulcahy
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History

• Every software development project has some risk
  associated with it. This could include advances
  in hardware or other software that would make a
  current project obsolete. Often times when
  perfectly good software is produced there may be
  no need for it, or something better has replaced
  it.
• In 1988 B.W. Boehm, proposed A Spiral Model of
  Software Development. The main feature being
  Risk Analysis being built into every phase of the
  model.
• The Spiral Model is based on the Waterfall
  method. However it is improved by the use of
  prototypes and risk analysis.

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• Waterfall Method Scenario
• You order a car by mail order. However, instead
  of getting pictures you receive a written
  description of the makes and models the company
  produces.
• A lengthy description would not be understandable
  to anyone except a computer.

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Why Risk Analysis?

• Consider A Real-Time System. During the Gulf
  War, an Iraqi Scud missle struck an American
  barracks in Saudi Arabia. 28 Americans were
  killed while another 98 were wounded.
• The cause? A Software Timing fault, which the
  Israelis corrected and installed only hours
  before a direct hit.

• If Better Risk Analysis and testing were used
  incidents like these could be avoided

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• Spiral Model Scenario
• A telephone company creates a new algorithm to
  route calls for a long distance network.
• If the algorithm fails the product cost will have
  exceeded its benefits, and customers will take
  their business elsewhere.
• By using a prototype to test the algorithm it
  minimizes this risk.

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Benefits of Spiral Model

• The Spiral Model emphasis alternative and reuse
  of software
• The incorporation of software quality is also a
  specific objective
• The prevention of ballooning costs and debts
• Maintenance is a built in into the development
  cycle

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Disadvantages of the Spiral Model

• The Spiral Model is not suited for in house
  projects
• The Model only works with large products, Risk
  analysis at every step doesnt make sense on
  small projects
• The Spiral Model requires competent risk analysis

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Spiral Model In Use

• In a test set of 25 projects that used the spiral
  Model, the productivity of every project
  increased by at least 50 over previous levels
  and by 100 in most projectsSchach, 1988.

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References

• http//www.stsc.hill.af.mil/crosstalk/1995/jan/Com
  paris.asp
• Stephen R. Schach, Software Engineering with
  Java, Tom Casson, 1997.
• B.W.Boehm, A Spiral Model of Software
  Development and Enhancement, IEEE Computer, May
  1988.
• P. Mellor, CAD Computer Aided Disaster,
  Technical Report, Center for Software
  Reliability, July 1994.