Welch's bridge

Welch's bridge is a term coined by Alexander Nicholi in reference to an excerpt of an article called Programming Sucks by blogger Peter Welch. The excerpt tells a story about a bridge building project, revealed at the end to be an analogy of what it is to do programming.

Excerpt text

Imagine joining an engineering team. You’re excited and full of ideas, probably just out of school and a world of clean, beautiful designs, awe-inspiring in their aesthetic unity of purpose, economy, and strength. You start by meeting Mary, project leader for a bridge in a major metropolitan area. Mary introduces you to Fred, after you get through the fifteen security checks installed by Dave because Dave had his sweater stolen off his desk once and Never Again. Fred only works with wood, so you ask why he’s involved because this bridge is supposed to allow rush-hour traffic full of cars full of mortal humans to cross a 200-foot drop over rapids. Don’t worry, says Mary, Fred’s going to handle the walkways. What walkways? Well Fred made a good case for walkways and they’re going to add to the bridge’s appeal. Of course, they’ll have to be built without railings, because there’s a strict no railings rule enforced by Phil, who’s not an engineer. Nobody’s sure what Phil does, but it’s definitely full of synergy and has to do with upper management, whom none of the engineers want to deal with so they just let Phil do what he wants. Sara, meanwhile, has found several hemorrhaging-edge paving techniques, and worked them all into the bridge design, so you’ll have to build around each one as the bridge progresses, since each one means different underlying support and safety concerns. Tom and Harry have been working together for years, but have an ongoing feud over whether to use metric or imperial measurements, and it’s become a case of “whoever got to that part of the design first.” This has been such a headache for the people actually screwing things together, they’ve given up and just forced, hammered, or welded their way through the day with whatever parts were handy. Also, the bridge was designed as a suspension bridge, but nobody actually knew how to build a suspension bridge, so they got halfway through it and then just added extra support columns to keep the thing standing, but they left the suspension cables because they’re still sort of holding up parts of the bridge. Nobody knows which parts, but everybody’s pretty sure they’re important parts. After the introductions are made, you are invited to come up with some new ideas, but you don’t have any because you’re a propulsion engineer and don’t know anything about bridges.

Would you drive across this bridge? No. If it somehow got built, everybody involved would be executed. Yet some version of this dynamic wrote every single program you have ever used, banking software, websites, and a ubiquitously used program that was supposed to protect information on the [web] but didn’t.

Significance

While the analogy was written in a context of irony, it has proven to be exceptionally useful in helping explain to people how exactly things have become so unreliable and expensive with software development. It was an early source of context for the reframing of software development as a more static, final practise – this would later become what is now known as mechanicalism.