Spiral model

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Spiral model (Boehm, 1988).
Software development process
Activities and steps
Requirements · Specification
Architecture · Design
Implementation · Testing
Deployment · Maintenance
Agile · Cleanroom · DSDM
Iterative · RAD  · RUP  · Spiral
Waterfall · XP · Scrum  · V-Model
Supporting disciplines
Configuration management
Quality assurance (SQA)
Project management
User experience design
Compiler  · Debugger  · Profiler
GUI designer
Integrated development environment

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. Also known as the spiral lifecycle model, it is a systems development method (SDM) used in information technology (IT). This model of development combines the features of the prototyping model and the waterfall model. The spiral model is intended for large, expensive and complicated projects.


[edit] History

The spiral model was defined by Barry Boehm in his 1988 article "A Spiral Model of Software Development and Enhancement"[1]. This model was not the first model to discuss iterative development, but it was the first model to explain why the iteration matters.[citation needed]

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.

[edit] The Spiral Model

The steps in the spiral model can be generalized as follows:

  1. The new system requirements are defined in as much detail as possible. This usually involves interviewing a number of users representing all the external or internal users and other aspects of the existing system.
  2. A preliminary design is created for the new system.
  3. A first prototype of the new system is constructed from the preliminary design. This is usually a scaled-down system, and represents an approximation of the characteristics of the final product.
  4. A second prototype is evolved by a fourfold procedure:
    1. evaluating the first prototype in terms of its strengths, weaknesses, and risks;
    2. defining the requirements of the second prototype;
    3. planning and designing the second prototype;
    4. constructing and testing the second prototype.

[edit] Applications

The spiral model is used most often in large projects. For smaller projects, the concept of agile software development is becoming a viable alternative. The US military has adopted the spiral model for its Future Combat Systems program.

[edit] Advantages

The spiral model promotes quality assurance through prototyping at each stage in systems development.

[edit] See also

[edit] References

  1. ^ Boehm B, "A Spiral Model of Software Development and Enhancement", "Computer", "IEEE", 21(5):61-72, May 1988
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