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2.3.2.2.2
Disadvantages
XP is framed as trying to solve the problem of software development risk with
a solution of people in the environment of a small project. XP's approach is
fragile and can fail if the project environment changes or the people change.
2.3.2.2.3
Suitability
Extreme programming is targeted toward small-to-medium-sized teams building
software in the face of vague and/or rapidly changing requirements.
2.3.2.3 Wheel and Spoke Model. The Wheel and Spoke Model is a se-
quential parallel software development model. It is essentially a modification of
the Spiral Model that is designed to work with smaller initial teams, which then
scale upward and build value faster. It is best used during the design and pro-
totyping stages of development. It is a bottom-up methodology. The Wheel and
Spoke Model retains most of the elements of the Spiral Model, on which it is
based.
As in the Spiral Model, it consists of multiple iterations of repeating activities:
1. New system requirements are defined in as much detail as possible from several
different programs.
2. A preliminary common application programming interface (API) is generated
that is the greatest common denominator across all the projects.
3. The implementation stage of a first prototype.
4. The prototype is given to the first program where it is integrated into their
needs. This forms the first spoke of the Wheel and Spoke Model.
5. Feedback is gathered from the first program and changes are propagated back
to the prototype.
6. The next program can now use the common prototype, with the additional
changes and added value from the first integration effort. Another spoke is
formed.
7. The final system is the amalgamation of common features used by the different
programs—forming the wheel, and testing/bug-fixes that were fed back into
the code-base—forming the spokes.
Every program that uses the common code eventually sees routine changes and
additions, and the experience gained by developing the prototype for the first program
is shared by each successive program using the prototype (Wheel and Spoke Model,
2008). The wheel and spoke is best used in an environment where several projects
have a common architecture or feature set that can be abstracted by an API. The core
team developing the prototype gains experience from each successful program that
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