Waterfall Model with Prototype

Why we had chosen Waterfall Model with Prototype, but not traditional Waterfall Model?

Weaknesses or disadvantages of traditional Waterfall Model in hand, as we decided not to choose it to be implemented to our group project:

• 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.
  It only incorporates iteration indirectly, thus changes may cause considerable confusion as the project progresses.
• For ever changing user requirements this model will not suit, one process starts only when the previous process comes to an end.
• 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.