29.tex

Try before choosing

Creating an application requires many decisions to be made. Some might involve choosing a framework or library while others revolve around the use of specific design patterns. In either case the responsibility for the decision generally lies with the architect on the team. A stereotypical architect might gather all the information that can be gathered, then mull over it for a while, and finally decree the solution from the ivory tower for it to be implemented by the developers. Not surprisingly there is a better way.

In their work on lean development Mary and Tom Poppendieck describe a technique for making decisions. They argue that we should delay commitment until the last responsible moment, that is the moment at which, if the team does not make a decision, it is made for them; when inaction results in an outcome that is not (easily) reversible. This is prudent because the later a decision is made the more information is available on which to base the decision. However, in many cases more information is not the same as enough information, and we also know that the best decisions are made in hindsight. What does this mean for the good architect?

The architect should constantly be on the look out for decisions that will have to be made soon. Provided the team has more than a handful of developers and practices collective code ownership the architect can, when such a decision point approaches, ask several developers to come up with a solution to the problem and go with it for a while. As the last responsible moment arrives the team gets together and assesses the benefits and drawbacks of the different soutions. Usually, now with the benefit of hindsight, the best solution to the problem is apparent to everybody. The architect does not have to make the decision, he or she merely orchestrates the decision making process.

This approach works for small decisions as well as for large ones. It can allow a team to figure out whether or not to use the Hibernate templates provided by the Spring framework but it can equally answer the question of which JavaScript framework to use. The duration for which the different approaches evolve is obviously very dependent on the complexity of the decision.

Trying two or even more approaches to the same problem requires more effort than making a decision upfront and then just implementing one. However, chances are that an upfront decision leads to a solution that is later recognized to be sub-optimal, leaving the architect with a dilemma: either the team rolls back the current implementation or they live with the consequences, both of which result in wasted effort. Even worse, it is entirely possible that nobody on the team recognizes that the approach chosen is not the best one, because none of the alternatives were explored. In this case effort is wasted without any chance of addressing the waste. After all, trying multiple approaches might be the least expensive option.

By Erik Doernenburg