…which stands for “you ain’t gonna need it” and is an important principle of Agile development, with strong benefits for the business.
The basis for YAGNI stems from a failure common in many software development projects: that when a developer creates a component of a system they tend to give it more flexibility than is immediately necessary, so that it can be reused in more contexts and provide more value. But the result in practice is almost always over-engineering: the component costs more to develop, the suspected additional use rarely materialises, when it does materialise it has requirements that don’t quite match the actual implementation, and the component as a whole is more brittle, less comprehensible to successive developers and more difficult to maintain.
By contrast YAGNI says “you ain’t gonna need it”: develop the absolute minimum to get it working for the immediate problem, and extend it later only if another specific needs arises. This works in Agile development because there is a wider supporting structure which enables changes to be made with minimal cost.
An excellent example of YAGNI in action was our implementation of content workflow. There are lots of things you could do with workflow. You can lock content to ensure that only one person can edit it at a time; you can branch content so that different versions can be worked on simultaneously; one of our senior stakeholders was keen on allowing numbered versions which she had seen elsewhere, allowing individual changes to be tracked and traced, and even allowing someone to switch back to a previous numbered version — but she did say that the feature was almost never used.
What we did in practice was a minimal workflow with minimal cost: we built in the ability to have content as draft and live, and very little more. That was sufficient for the staff who we knew would be using it. It seems like we could have taken the opportunity to build more, in case more people with more needs would use it. But you know what they say — you ain’t gonna need it. In the months following that very early stage in the project the company changed a lot, and among other things this included much more integrated working between editorial teams who were previously designated “web” or “print”… these days that distinction has diminished. The technological impact is that many editorial staff are using an integrated front-end, sitting outside the web system, and that’s where the workflow is handled now.
The industry-wide drive for integrated publishing changed our working environment; if we’d have developed elaborate workflow in the web system it would have been wasted effort, and a large wasted cost for the company.