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 was defined by Barry Boehm in his article
A Spiral Model of Software Development and Enhancement
from . This model was not the first model to discuss
iterative development, but it was the first model to
explain why the iteration matters. As originally envisioned,
the iterations were typically months to 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.
The Spiral model is used most often in large projects
(by companies such as IBM and Microsoft) and needs constant
review to stay on target. 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.
Advantages
Estimates (i.e. budget, schedule, etc.) get more realistic
as work progresses, because important issues are discovered
earlier.
It is more able to cope with the (nearly inevitable)
changes that software development generally entails.
Software engineers (who can get restless with protracted
design processes) can get their hands in and start working
on a project earlier.
From
Wikipedia
