Linked by Thom Holwerda on Tue 9th May 2006 21:25 UTC, submitted by luzr
OSNews, Generic OSes Torvalds has indeed chimed in on the micro vs. monolithic kernel debate. Going all 1992, he says: "The whole 'microkernels are simpler' argument is just bull, and it is clearly shown to be bull by the fact that whenever you compare the speed of development of a microkernel and a traditional kernel, the traditional kernel wins. The whole argument that microkernels are somehow 'more secure' or 'more stable' is also total crap. The fact that each individual piece is simple and secure does not make the aggregate either simple or secure. And the argument that you can 'just reload' a failed service and not take the whole system down is equally flawed." My take: While I am not qualified to reply to Linus, there is one thing I want to say: just because it is difficult to program, does not make it the worse design.
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The COSA model is a synchronous model. It is the same model used by logic circuits. Essentially, COSA transforms software into a signaling system comparable to hardware. My claim is simple and is not an extraordinary claim that requires extraordinary proof: if logic circuits can be proven correct, so can COSA programs.

But that answers nothing. I can chain some simple conditional statments together and make a provably correct program. A sufficiently large collection of these can conceivably handle any software problem. But, the whole problem becomes one of the programmer's conception, rather than whether the if-then-else statements actually do what they are supposed to. I don't see how a signal-based program can escape this scenario. May as well try to escape logic altogether.

And by the way, I wasn't asking whether your model is "provably correct", but whether it is provably superior. Big difference. It may have seemed like a non-sequitor, but I brought up the relational model because it is a perfect example of the sort of thing the programming world should be striving towards: an expression of logic in programming that has complete conceptual integrity. I believe it can be demonstrated through logic to be provably superior to any other method of data management created. That sounds like a big claim, but I make it due to a simple syllogism:

1. Logic is the ideal tool to handle computational tasks, since it is the only way to prove correctness at any level.

2. The relational model is simply a complete application of logic to data management, allowing one to express any and all manipulations of data in a logically consistent way.

3. Thus, the relational model is the ideal data management tool, and any deviation from that is only an undesirable limitation.

(For any who want to flame me for this, at least please do yourself the credit of spending some time thinking about this syllogism first)

Within the scope of data management, the relational model allows one to create systems that are provably correct, through data definition and constraints, allowing one to express exactly what should and should not be allowed to happen to the data. Now the problem with the relational model is one of implementation--namely that it has never been truly implemented, and the systems that exist almost all allow grievous violations and circumventions of the logic that one might express. But at the conceptual level it has that certain... completeness.

I fail to see any such conceptual integrity or completeness in the greater scope of programming paradigms, including the COSA model. I'm waiting for it anxiously, and just not seeing it. I think functional programming may be the closest we have come to that sort of thing in the programming world, but it still seems disappointingly difficult to handle any but the most self-contained, algorithmic sorts of tasks. Meanwhile, I still maintain that whether your programming is signal-based, algorithmic, functional, object-oriented, monolithic, distributed--whatever, you still can't escape the fact that complex logical systems are difficult to prove correct, and the more complex they become, the closer you come to requiring an infinite amount of time simply to *make* the proof. It is not a limitation of the paradigm, but of the human mind itself. I don't see any way around it any more than there is a way to escape the scenario we live in called "universe" (to paraphrase Buckminster Fuller).

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