by Leon Rosenshein

Design Is Iterative

I’ve talked about rework avoidance and the advantage of taking smaller steps. I’ve talked about how it’s different from the older BDUF process. How a sea chart gives you a better chance of getting a successful result.

Given that, and, the fact that the Agile Manifesto, was written in 2001, you would think that the concept of iterative design is a new one.

However, you’d be wrong.

Way back in 1968, in the Software Engineering Report by the NATO Science Committee, you’ll find this quote by H. A. Kinslow.

The design process is an iterative one. I will tell you one thing which can go wrong with it if you are not in the laboratory. In my terms design consists of:

  1. Flowchart until you think you understand the problem.
  2. Write code until you realize that you don’t.
  3. Go back and re-do the flowchart.
  4. Write some more code and iterate to what you feel is the correct solution

There are a lot of good ideas in that report, but Kinslow’s comment really resonates with me. It plays well with my personal bias for action. Do some planning. Write some code. Repeat. Or put another way, learn from the domain to write some code. Then learn from the code to better understand the domain. Then do it again. By learning from both, iteratively, you come up with a better answer then only learning from either one. And, you’ll probably come to that answer sooner.

It’s a system. A system with at least 2 loops. The questioning/understanding loop and the building loop. At first you don’t even know what questions to ask. You start with a problem statement. You think you understand it well enough to write a solution, but then you have questions. So you dig deeper and get your questions answered. Which leads to more understanding and a better solution, which leads to more questions. The cycle repeats until you have enough understanding to build a solution that actually solves the original problem.

So remember, whether it’s your APIs, your class design, your domain boundaries, or how your systems work together, iteration is your friend. Because without iterating you can’t have enough understanding to come up with a good solution.