- Spiral model
The spiral model is a
software development process combining elements of bothdesign andprototyping -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 ininformation technology (IT). This model of development combines the features of the prototyping model and thewaterfall model . The spiral model is intended for large, expensive and complicated projects.History
The spiral model was defined by
Barry Boehm in his 1988 article "A Spiral Model of Software Development and Enhancement" [Boehm B, [http://www.cs.usu.edu/~supratik/CS%205370/r5061.pdf "A Spiral Model of Software Development and Enhancement] ", "Computer", "IEEE", 21(5):61-72, May 1988] . This model was not the first model to discussiterative development , but it was the first model to explain why the iteration matters.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 projectThe Spiral Model
The steps in the spiral model can be generalized as follows:
# The newsystem 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.
# A preliminary design is created for the new system.
# A firstprototype 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.
# A second prototype is evolved by a fourfold procedure:
## evaluating the first prototype in terms of its strengths, weaknesses, and risks;
## defining the requirements of the second prototype;
## planning and designing the second prototype;
## constructing and testing the second prototype."'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. TheUS military has adopted the spiral model for itsFuture Combat Systems program.Advantages
The spiral model promotes quality assurance through prototyping at each stage in systems development.
ee also
*
Software engineering
*List of software engineering topics
*Waterfall model
*Chaos model
*MBASE
*V-model
*Dual Vee Model References
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