Charting risk and incremental development

Big bang risk chartHere’s a visualisation, which I find useful, to describe the risk inherent in big bang releases.

A big bang release of a big tech project is often superficially more desirable than an incremental release—it’s surprises the world and makes more of a statement. It’s something you can hang some tangible PR around. Incremental releases are typically much less risky, and mean you’re more likely to end up with what you want, because you can accept feedback. But incremental releases often also involve more work—they require a mechanism to make incremental changes, and many architectures don’t have that built in. I’ve written about these issues before, in more detail.

The chart here explains the trade-offs. The x-axis shows time. The area under each curve is the probability of the release completing (with all issues resolved) in any given period.

The red vertical shows the estimated big bang completion. Theoretically it’s earlier than the estimated release of the incremental approach (the black vertical). But in reality the big bang release is likely to be much later. Its range of uncertainty is much greater, and spreads out much later.

Sometimes words work well explaining trade-offs. I find this chart useful if you need a more visual explanation.