Muli Ben-Yehuda's journal

September 30, 2005

Filed under: Uncategorized — Muli Ben-Yehuda @ 1:55 AM

Linus on specifications. All I can say is – amen. The rest of the thread is amusing in a horrifying way, an Adaptec guy ranting and raving and Just Not Getting It. If this is any indication of Adaptec engineers… I know which storage vendor I will not be buying from.

How we do the SW is indeed up to us, but I want to step in on your first point.

Again.

A “spec” is close to useless. I have _never_ seen a spec that was both big enough to be useful _and_ accurate.

And I have seen _lots_ of total crap work that was based on specs. It’s _the_ single worst way to write software, because it by definition means that the software was written to match theory, not reality.

So there’s two MAJOR reasons to avoid specs:

– they’re dangerously wrong. Reality is different, and anybody who thinks specs matter over reality should get out of kernel programming NOW. When reality and specs clash, the spec has zero meaning. Zilch. Nada. None.

It’s like real science: if you have a theory that doesn’t match experiments, it doesn’t matter _how_ much you like that theory. It’s wrong. You can use it as an approximation, but you MUST keep in mind that it’s an approximation.

– specs have an inevitably tendency to try to introduce abstractions levels and wording and documentation policies that make sense for a written spec. Trying to implement actual code off the spec leads to the code looking and working like CRAP.

The classic example of this is the OSI network model protocols. Classic spec-design, which had absolutely _zero_ relevance for the real world. We still talk about the seven layers model, because it’s a convenient model for _discussion_, but that has absolutely zero to do with any real-life software engineering. In other words, it’s a way to _talk_ about things, not to implement them.

And that’s important. Specs are a basis for _talking_about_ things. But they are _not_ a basis for implementing software.

So please don’t bother talking about specs. Real standards grow up _despite_ specs, not thanks to them.

Linus

Filed under: Uncategorized — Muli Ben-Yehuda @ 1:24 AM

Mission accomplished. I’m going home now ๐Ÿ™‚

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