Sunday, 6 December 2015

Think how big the box is before you build a wedding cake

The waterfall (fixed features) vs agile (fixed time) question is not new one but it's one that affects all levels of an organisation and hence buy-in at the top is important. I was recently trying to explain to someone in automotive that while the principle of applying systems engineering is the right one, the process proposed needs careful consideration.

Firstly, consider the project management triangle of time, cost and features. This tells us that if we have more time we can have more features. If we have more cost then it will take us less time. We can't have more features for less time. There are caveats, of course, but the model makes sense. We can only control two of the sides.

In aerospace, features (i.e. quality/scope) is often a greater driver. We can't incrementally get the plane flying and add the wings later. Whereas in automotive the time is often fixed as an OEM doesn't want ship a vehicle to fit a software development life-cycle, it has a regular model-year cycle.

What this tells us is that there is no value in coming up with the most brilliant wedding cake of desire if it won't fit into the box that we need to send it in. Fundamentally we need to design a series of cakes that do fit into boxes or, in other words, a spiral or iterative method is needed. Invariably this means that it's best to consider time as fixed from the outset, and define features that are possible with the available resource.