Evolutionary design still requires up front thinking

There's a great post by Joshua Kerievsky titled The Day We Stopped Sprinting that itself references an older post called Evolutionary Design, which talks about the need to create a "primitive whole" initially, before iterating to improve it over time. The important thing to note here is that the primitive whole isn't just a bunch of unassembled parts, it's a "under-developed whole" and something that does work (to some extent, anyway). The example used in the illustration is a guitar, with the first version being something that looks like a very primitive guitar.

Something that's often missed here, or not discussed explicitly, is that you still need to do some up front thinking in order to get to that primitive whole, and to create an initial vision or starting point. After all, the primitive guitar is still a guitar, which implies that somebody somewhere had a vision early on that a guitar was the thing that was needed. In my experience, I've seen many teams misinterpret "evolutionary design" and "emergent architecture" to mean, "you don't need to do any design up front at all". As Dave Thomas says, "big design up front is dumb, but doing no design up front is even dumber".

During my software architecture workshops, I occasionally see teams draw nothing more than a visual summary of the requirements when asked to work in groups and design a software solution. The requirements are based upon a "financial risk system" for a bank, and sometimes groups will literally just draw a box labelled "Financial Risk System" before proudly proclaiming, "that's all of the up front design we need to do, we're agile". Yes, this really has, and still does happen from time to time.

Engaging with the problem

Many years ago, my boss gave me a small internal software project to work on. I don't remember the exact details, but he basically gave me a problem statement and told me to design a software solution. After a couple of hours, I presented my solution. It was instantly ripped apart and he told me that I hadn't properly engaged with the problem. He was right. I'd presented a very simple solution that didn't cater for any of the complexity of the problem space, mainly because I hadn't actually uncovered it yet. On my travels around the world, I regularly see the same thing, and people really struggle with the concept of doing up front design. Many of them also never really engage their minds in the problem, evidenced by one or more diagrams that present a very simplified and superficial view of the solution, such as the typical "logical view" diagrams below.

An example software architecture diagram

Whenever I'm doing an up front design exercise, I want it to be quick and efficient while still providing as much value as possible. The process of doing some up front design provides you with a way to engage with the problem space and create a starting point for your vision of the thing you want to build. For me, doing up front design is about understanding the structure of the thing you're going to build, creating a starting point and vision for the team to work with and identifying/mitigating the highest priority risks. As I've discovered, a simple way to make this happen is to encourage people to actually produce some lightweight yet structured artifacts, like the diagrams in my C4 model, as a part of the design process. When they do this, conversations change because it forces people to engage with the problem. Up front design is therefore a crucial part of a longer evolutionary design process. Without it, you're just lost.

About the author

Simon is an independent consultant specializing in software architecture, and the author of Software Architecture for Developers (a developer-friendly guide to software architecture, technical leadership and the balance with agility). He’s also the creator of the C4 software architecture model and the founder of Structurizr, which is a collection of open source and commercial tooling to help software teams visualise, document and explore their software architecture.

You can find Simon on Twitter at @simonbrown ... see simonbrown.je for information about his speaking schedule, videos from past conferences and software architecture training.