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Comment by teo_zero | Hacker News Reader

What has always baffled me is how CS uses the word "safety" where all other industries use "robustness".

A robust design is one that not only is correct, but also ensures the functionality even when boundary conditions deviate from the ideal. It's a mix of stability, predictability and fault tolerance. Probably "reliable" can be used as a synonym.

At the same time, in all industries except CS "safety" has a specific meaning of not causing injuries to the user.

In the design of a drill, for example, if the motor is guaranteed to spin at the intended rpm independently of orientation, temperature and state of charge of the battery, that's a robust design. You'll hear the word "safe" only if it has two triggers to ensure both hands are on the handles during operation.

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You use safety more in relation to correctness aspects of algorithms. Some safety properties you can actually prove. When it comes to robustness it is more about dealing with things sometimes being incorrect regardless of the safety mechanisms. So, a try catch for something that isn't actually expected to normally fail makes you robust against the scenario when that does fail. But you'd use e.g. a type system to prevent classes of failures as safety mechanism.

It's a very soft distinction, I agree. And possibly one that translates less well to the physical world where wear and tear are a big factor for robustness. You can't prove an engine to be safe after thousands of hours. But you can make it robust against a lot of expected stuff it will encounter over those hours. Safety features tend to be more about protecting people than the equipment.

Without any context safety _can_ mean a lot of things, but it's usually used as a property of a system and used alongside liveness.

Basically, safety is "bad things won't happen" and liveness is "good things eventually happen".

This is almost always the way safety is used in a CS context.

> What has always baffled me is how CS uses the word "safety" where all other industries use "robustness".

FWIW "safety factors" are an important part of all kinds of engineering. The term is overloaded and more elusive in CS because of the protean qualities of algorithmic constructs, but that's another discussion.

I think in things like philosophy/debate/etc it's common to talk about "safe assumptions". I always figured that's the metaphor being leaned on here.

I agree it's confusing when you step outside of CS world though.

> At the same time, in all industries except CS "safety" has a specific meaning of not causing injuries to the user.

That makes sense, as CS is transversal to industries. Same practices that can contribute to literally save lifes in one domain will just avoid minor irritating feeling in an other.

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