[mannykannot]

A while back, I visited a facility that builds prefabricated houses. Using CAD, they can, and do, create large and architecturally complex one-off designs, something that would not be possible without knowing not only the final (as-constructed) design, but the intermediate states as the modules are constructed, moved to the site (including ensuring that they can be moved to the site), and assembled.

I don't suppose that everything works entirely according to plan, and of course there is no way that every future change request can be anticipated, let alone accommodated in advance, but for all practical purposes, this shows that if one is prepared to do what it takes, one can start the construction of a house knowing what you are going to get and with a detailed plan for getting there.

Computational technology has a particularly broad and active leading edge where unknowns are being tackled, but even so, most software development is nowhere near that edge.

The original point about houses is that with software, similar-seeming changes can have greatly differing costs, on account of what is hidden from the users' view, and I think the analogy works very well in making that point.