[twh270]

I think the only way this gets better is with software development tools that make it impossible to create invalid states.

In the physical world, when we build something complex like a car engine, a microprocessor, or bookcase, the laws of physics guide us and help prevent invalid states. Not all of them -- an upside down bookcase still works -- but a lot of them.

Of course, part of the problem is that when we build the software equivalent of an upside down bookcase, we 'patch' it by creating trim and shims to make it look better and more structurally sound instead of tossing it and making another one the right way.

But mostly, we write software in a way that allows for a ton of incorrect states. As a trivial example, expressing a person's age as an 'int', allowing for negative numbers. As a more complicated example, allowing for setting a coupon's redemption date when it has not yet been clipped.

[bunderbunder]

John Backus's Turing Award lecture meditated on this idea, and concluded that the best way to do this at scale is to simply minimize the creation of states in the first place, and be careful and thoughtful about where and how we create the states that can't be avoided.

I would argue that that's actually a better guide to how we manage complexity in the physical world. Mechanical engineers generally like to minimize the number of moving parts in a system. When they can't avoid moving parts, they tend to fixate on them, and put a lot of effort into creating linkages and failsafes to try to prevent them from interacting in catastrophic ways.

The software engineering way would be to create extra moving parts just because complicated things make us feel smart, and deal with potential adverse interactions among them by posting signs that say "Careful, now!" without clearly explaining what the reader is supposed to be careful of. 50 years later, people who try to stick to the (very sound!) principles that Backus proposed are still regularly dismissed as being hipsters and pedants.

[int_19h]

I'd say that the extra moving parts are there in most cases not because someone wanted to "feel smart" (not that it doesn't happen), but to make the pre-existing moving parts do something that they weren't originally supposed to do, because nobody understands how those pre-existing parts work well enough to re-engineer them properly on the schedule that they are given. We are an industry that builds bridges out of matchsticks, duck tape, and glue, and many of our processes are basically about how to make the result of that "good enough".

[james_marks]

To determine what states should be possible is the act of writing software.