Much is said about agile approaches mostly in contrast of conventional waterfall methods. This blog is just a quick side to side comparison, but I would like to show you on when to apply them and when not. Both waterfall and agile approaches can be used for software development, infrastructure engineering and even any other project which needs to manage problems into solutions in a controlled way.

Both of the method types can be used with great success and don’t believe in the fact that one is better then the other, it is just the environment that might prefer one above the other.

Waterfall

Waterfall is a method where all steps are done in a sequence, these phases are defined and when one is done the other takes of. Of course they can be used with techniques as iterations to go back to earlier phases to refine the work, but once the phase is closed the next one starts. Normally in organisation different departments sign of these phases to all commit on the contents. Basically the process moves from collecting requirements, to specification and design into the solutions area for implementation and operating. Each step moves more towards realisation and operating, or from problem definition into solution.

Waterfall is a great approach when both the problem and solution area are predictable and stable, that means that with defined steps it is possible to properly select solutions. This approach requires environments where problem areas are also stable, meaning that requirements won’t change over time. The picture below shows the approach in the dimension of problem and solution area.

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When the solutions area is known (meaning we have experience, done it before) and we are working inside a problem area which is known (been there done that) waterfall might be a good idea. Experience with both problem and solution areas are essential when selecting the waterfall model, that also means that lessons learned from the past need to be included to make it a “known” area. If a problem or solution space is an unknown territory it is clear that risk is introduced, either consciously or unconsciously.

One of the most risky things about Waterfall approach is that risk needs to be managed properly, this as much of the previous phases are closed and therefor all the next phases will just be a further realisation of the previous phases. Risk might therefore be building up. If things change over time, like requirements, or for instance aspect in the design are overlooked there might be issues introduced into future phases. It is clear that in such cases each phase will just be an add up of all these risks leading to huge problems during for instance implementation or operation. And this is where agile comes in.