Noel Rappin Writes Here

An Agile Musing

Posted on May 25, 2007

Of course, since I muse in an agile way, I reserve the right to change my mind based on future developments…

Software development usually takes place in a complex environment where your goal can change quickly. In general, there are two ways to deal with a complex environment. One is to try to anticipate, in advance, every possible permutation you might need to deal with, and the other is to manage your environment with the flexibility to respond to new challenges with minimum effort. Software is just a specific case where that challenge plays out.

Of course, being software engineers, we’ve given these approaches names. They are nicely defined by James Bach:

agile methodology : a system of methods designed to minimize the cost of change, especially in a context where important facts emerge late in a project, or where we are obliged to adapt to important uncontrolled factors.

A non-agile methodology , by comparison, is one that seeks to achieve efficiency by anticipating, controlling, or eliminating variables so as to eliminate the need for changes and associated costs of changing.

It seems worth pointing out that, at least in theory, there’s no reason why you can’t both make a reasonable effort to find potential changes up front, and still make your working environment as flexible as possible.

In practice, of course, this is kind of difficult to do well. There’s a logistics problem – the kinds of things you do when you’re trying to control change up front generally involve creating a lot of models and documentation and the like. This is exactly the kind of thing that works against minimizing the cost of change. But it seems to me that a group determined to do some up front analysis of what will largely be an agile process could manage to work around that.

The bigger problem is an issue of mindset – if you think that you can solve all your design problems up front, then you start to look at any change to the design or implementation with suspicion. At that point, any change is, by definition, a mistake of some kind. Which leads to suspicion of all changes and can mean all kinds of tracking and procedural overhead that pushes up the cost of change. The sort of organic, bottom-up design that you get from test-first and tight iterations doesn’t fit in this model at all.

Although I should say that in my experience trying to get groups to adopt XP or agile practices over several different companies is that nearly all programmers and managers agree that automated tests are a good thing. Most programmers are at least willing to consider the idea of test-first, although getting somebody to do it consistently is tough (hey, it’s tough even for somebody who’s totally bought into it).

The resistance I do get tends to be around the idea that you can start programming with an incomplete design without it leading to disaster.

Waterfall-style up front design can be incredibly seductive. You’re brainstorming with other smart people, you’re solving all your problems before they even come up. It certainly feels like you are doing something vitally important to the success of your project. Even if you know that many of the decisions will later be revised in implementation, it still feels good to have that crisp UML diagram. You can’t have bugs in a UML diagram. The issues that do get solved in design are assumed to justify the time cost of the design, because the assumption is that the time cost of later improvements will be much larger (which is true, in part, because of the amount of design work).

In contrast, starting coding with incomplete information can feel risky, especially the further you get from the actual implementation team. Any issue that gets changed later can be blamed on the relative lack of design, true or not, and the time savings from not doing as much design can be invisible. It’s very hard to let go of the idea that all your design problems can be solved up front. But once you are willing to allow that some problems can only be solved in the moment, you’re much better equipped to deal with the inevitability of change.


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