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Comment by Spooky23 | Hacker News Reader

Exactly.

“Idempotent” is one of the key words used as a cudgel in this way. It’s great for the bullshit artist, as to a layman the dictionary definition is completely inscrutable.

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> as to a layman the dictionary definition is completely inscrutable.

This isn't written for laymen, who would obviously never be reading about what SystemD is. It's written for specialists who do engineering work on or with Linux, and who actually need to know the technical details of their tools.

And anyway, I suspect plenty of laymen, and highly trained professionals in other fields like law, medicine, and philosophy among others, would have no trouble understanding what "idempotent" is. It's not inscrutable at all, but rather is one of the easiest concepts in CS and software engineering to understand.

Idempotence is a desirable property of systems whereby repeating an action has no effect. Mathematically, an operator is idempotent if f(f(x)) = f(x).

Idempotence is handy because it implies that one can retry safely if one isn't sure whether something succeeded or failed. Not sure if your file was saved? Save again! If it was indeed saved, the file continues to be saved. If the file was not saved, it is now. Yay.

I would kill for such descriptions of every system I work with.

Idempotent is surely a valuable piece of software jargon. I know exactly what the user intends, and have good ideas of how hard it is and what likely trade offs they will be making behind the scenes

surely it is the very opposite of bullshit.

But the phrase in the paragraph is non-idempotent which is completely redundant. Every piece of software in the world is non-idempotent.

Apart from the idempotent ones ... :-)

Idempotent is a perfectly fine word. There is absolutely no reason why CS shouldn't have it's own jargon. I found the description very descriptive.

"I found the description very descriptive" - an idempotent system in action.

Actually, it is just a word to describe the property that if you do something repeatedly, it leads to the same result as doing it just once. So the latter executions don't change anything.

And because it is such a common property when talking about algorithms and APIs the word is pretty common among CS people.

One very popular example are REST APIs because some HTTP verbs are idempotent and others are not [1]. This is also the reason why your browser asks you, if you want to submit a form again when refreshing a page that has been reached by submitting a POST-form.

[1] https://en.wikipedia.org/wiki/Representational_state_transfe...

> Exactly.

> “Idempotent” is one of the key words used as a cudgel in this way. It’s great for the bullshit artist, as to a layman the dictionary definition is completely inscrutable.

Are you saying that being "idempotent" is completely inscrutable? Is it not a fairly straight-forward concept?

If we're going to be pedantic, "idempotent" (or rather non-idempotent) as used in the description is rather vapid and meaningless. Idempotency is a quality that describes the result of an action; as such, only actions can be thought of as idempotent. Applying the word idempotent to any noun that does not describe an action (such as "dataflow" in this case) is meaningless.

What does it mean for a dataflow to be idempotent in the first place? What purpose does it then serve to describe a dataflow as non-idempotent? What they meant to say, I guess, is that the dataflow may contain multiple actions for the same unit, and that systemd makes no guarantees about the end state of the unit in such a case. But even then, it is the execution which should be described as non-idempotent, and not the dataflow.

That feels unnecessarily pedantic. If the sole job of entity X is to perform action Y, and it always performs this action idempotently, then why not describe X as idempotent? It's shorter, and it's clear enough. It might not be precisely accurate in the dictionary definition of the word - but natural languages also have DSLs, and those DSLs evolve to adapt to their use cases. Saying "thing that performs an idempotent action" over and over again is a waste of everybody's time.

In the context used, it’s fluff.

Idempotent is a perfectly cromulent word for a technical article not aimed at complete newbies.

Idempotent is a very clear and quite basic term: being able to run something multiple times with no different outcome than running it once. A very valuable property for certain systems (even for simple shell scripts).

And the description of systemd just uses bog standard terms related to what systemd does and the resources it manages.

But I get the feeling that both this and the parent comment it agrees with were more about the putdown and talking bad at someone, than about a technical or other objection.

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