When Not To Iterate

comments edit

As a kid, one of my favorite tools I had was a shiny red cased Victorinox swiss army knife. I’d carry that sucker around with me everywhere, using the main blade to tackle nearly every problem like a caveman with a stick. Until one day I sliced my finger trying to stick a paper cup to a tree so we could throw ninja stars at it, but that’s a story for another time.

As software developers, we have a swiss army knife of approaches to tackling any given problem. And often, we like to pull out the same blade over and over again. For example, one tool that we pull out nearly all the time is the tool of “iterative” development.

As Atwood said in the comments to Micah’s post on harmful requirements, you gotta go “iterative”.

However, sometimes you really do need to pull out a different tool in your swiss army knife. For large projects, breaking it up into phases and iterations makes sense most of the time, but there are times where an iteration itself may be longer than other iterations. Sometimes such an iteration itself becomes a mini project that requires BDUF.

Here’s a scenario to chew on. Suppose an iteration of the project is to produce a report based on data imported from a couple external sources. The report only has to produce a single number based on a calculation applied to the data. This is the type of problem that may not lend itself well to iteration. The client is interested in the final number, not any number in between.

Sure you can have an iteration in which you mock up the report to show the client to get something in front of them, but even this can be dangerous because you’ve set the expectation that you can deliver the report. But do you know that until you’ve analyzed the data?

This is a situation we found ourselves in. The requirements appeared to be describing a specific calculation we needed to produce. But after a careful look at all the fields we were getting in, the data required to produce that report just isn’t there. And we won’t be getting that data. Yet we have to produce this report by Monday. It seems we’ve walked to the blackboard to solve a series of two equations, but each equation has three variables. “Does Not Compute”

It seems to me that this is a classic situation where some up front analysis would have saved our butt and set expectations properly. Unfortunately, we weren’t brought in to this project till later and had to take it on faith that the analysis had occurred, but it was lacking. Someone, anyone, should have looked at the columns of data we would be receiving, and reconciled the data with the calculation we would be producing. I’m not sure how we can iterate ourselves out of that problem.

In our situation, it may well be that the real calculation we need to produce is much simpler and less useful than the one we thought we were going to produce. So we may be out of the fire on this one. But should the stakeholder disagree, we’ve got issues.

Comments