he weekness of the Waterfall Model is at hand:
- It is very important to gather all possible requirements during the
first phase of requirements collection and analysis. If not all requirements are obtained at once the subsequent
phases will suffer from it. Reality is cruel. Usually only a part of the requirements is known at the beginning and
a good deal will be gathered during the complete development time.
- Iterations are only meant to happen within the same phase or at best from the start of the subsequent phase back to the
previous phase. If the process is kept according to the school book this tends to shift the solution of problems into later
phases which eventually results in a bad system design. Instead of solving the root causes the tendency is to patch
problems with inadequate measures.
- There may be a very big "Maintenance" phase at the end. The process only allows for a single run through the waterfall.
Eventually this could be only a first sample phase which means that the further development is squeezed into the last never
ending maintenance phase and virtually run without a proper process.
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