Earlier this year the term Hayim Makabee proposed the term 'Adaptable Design Up Front' as a way of pointing the way forwards between the Scylla of BDUF and the Charybdis of degenerating into a Ball of Mud.
Others have used the term 'Just Enough Design Up Front.' But what counts as just enough?
That's the wrong question. Because 'just enough' is an insight that misdirects you. Design is not a scalar quantity like length. There is no amount of up-front design that is the right amount. The question is, what are the useful bits of design to do up front?
And this is what 'Adaptable Design Up Front' addresses. What you must do up-front is support the change and development to come — usually growth or change in functionality — whilst nailing down the things that ought to be fixed: the invariants which give stability so that developers don't have to re-learn the system from scratch each day they come into work.
So the basic idea is this: you want just the up-front design that helps you to draw lines between things that will change frequently and things that remain stable over time.
So how to do it?
For the 3 minute kick-start, Hayim has an excellent set of slides to get you going. His 'architecture vs interior design' analogy and the idea of applying the open/closed principle at the architecture level hit that 'brilliantly simple' spot that make it all seem obvious in hindsight.
For more detail on designing for what changes vs. what stays stable, I seriously recommend Jim Coplien & Gertrud Bjørnvig's under-rated book Lean Architecture: for Agile Software Development which contains decades of hard thought and wisdom. They know the pitfalls on the way first-hand and they can help you navigate them. More important, they show how to prioritise the human factors in your technical architecture. Which, as every architect knows, is what really matters.