That's interesting, thanks; as you point out, an important aspect of software- as with building architecture is that it tends to evolve over time, and that's where the waterfall approach falls down. However, in software at least, it's not actually necessary to exchange one extreme for another - waterfall or agile; one can take benefits from both approaches, blending foresight and forward planning with modular construction.

> There are many advantages to building a house one room at a time.... It's more "agile"... The downsides are that the services and structure are a hodgepodge of eras and necessity... it may be infeasible to undertake a whole-house project like running ethernet to every room.

The thing is that that end result is actually the opposite of agile, being as it is more difficult to change, and this speaks more broadly to a perennial problem in software development - requirements change regularly, even deep into project development. Planning a design up front does not mean just fixing a specific set of requirements in stone, but also anticipating the things that may change, even without knowing the specifics of what those changes will be, and designing in a flexible way that can accomodate a broad spectrum of possible futures. A car manufacturer might conceivably branch into making other types of vehicles, plant equipment, and similar things like that, whereas they are unlikely to ever get into catering (and if they did, that would likely be a seperate business and a new piece of software). Responding only to the requirements in front of you right now tends to make the design more rigid rather than less, and almost inevitably leads to big balls of mud and big-bang rewrite projects that fail as often as they succeed. Keep in mind also that most software spends most of its life in maintenance mode, so optimising for the delivery stage is short-sighted at best.

Designing software in the way I'm describing is not easy, but it's definitely possible, and in my opinion offers a lot more value than it might first appear.

> A car manufacturer might conceivably branch into making other types of vehicles, plant equipment …

Do you consider mattresses "similar things like that" ?