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The next process model I want to discuss is evolutionary
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prototyping, which works in four main phases. We start
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from an initial concept, then we design and implement
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a prototype based on this initial concept, refine the prototype
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until it is acceptable, and finally we complete and
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release the prototype. Therefore, when developing a system using
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evolutionary prototyping, the system is continually refined and rebuilt.
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So it is an ideal process when not all requirements
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are well understood. Which is a very common situation. So, looking
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at this in a little more details, what happens is that
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developers start by developing the parts of the system that they
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understand, instead of working on developing a whole system, including parts
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that might not be very clear at that stage. The partial
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system is then shown to the customer and the customer feedback
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is used to drive the next iteration, in which either changes
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are made to the current features or new features are added.
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So, either the current prototype is improved or the
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prototype is extended. And finally, when the customer agrees that
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the prototype is good enough, the developers will complete all
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the remaining work on the system and release the prototype
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as the final product. So let's discuss as we did
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for the previous process models, what are the main advantages
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and disadvantages of evolutionary prototyping. In this case, the main
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advantage is the immediate feedback. Developers get feedback immediately as
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soon as they produce a prototype and they show it to
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the customer and therefore, the risk of implementing the wrong system is
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minimized. The main negative is the fact that it's difficult to plan.
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When using evolutionary prototype it is difficult to plan in advance how
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long the development is going to take, because we don't know how
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many iterations will be needed. And another drawback is that it can
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easily become an excuse to do kind of do cut and fix
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kind of approaches in which we hack something together, fix the main
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issues when the customer gives us feedback, and then continue this
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way, until the final product is something that is kind of
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working, but it's not really a product of high quality. Something
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else I want to point out before we move to the next
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software process model is that there are many different kinds of
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prototyping, so evolutionary prototyping is just
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one of them. For example, throwaway
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prototyping is another kind of prototyping in which the prototype is
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just used to gather requirements, but is thrown away at the end
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of the requirements gathering, instead of being evolved as it happens here.
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