Maybe you can ask a question - why should I need an analysis for my software project? Isn't it this the responsibility of the software author? There is an analogy: if you want to build a house, you will also need a plans before you make a first dig in the ground. And usually, you want to know how the house will look like in advance and that is why you hire architects and engineers.
Well, with software it is the same.
Palvelut