Re: Object-relational impedence

From: Eric <>
Date: Thu, 6 Mar 2008 14:58:35 +0000
Message-ID: <>

On 2008-03-05, Dmitry A. Kazakov <> wrote:
> On Wed, 5 Mar 2008 11:34:05 +0000, Eric wrote:
>> On 2008-03-04, Dmitry A. Kazakov <> wrote:
>> I don't believe that merely using an RDBMS will solve all problems. What
>> I meant was that, accepting what David said above, if you keep your data
>> in an RDBMS, it will be easily available for the solution of any
>> possible problem that can be solved using that data.
> No, this as well is wrong. Keeping "data" in RDBMS puts certain
> restrictions on what can be stored there and how it can be used later.

No it doesn't, in either case.

> You propose a solution (DB on a RDBMS). What was the problem? From your
> description the problem looks like a persistence layer. This what c.d.t.
> people vehemently disagree. Isn't it interesting to see how quickly a great
> theory of all degrades to storage?

A persistence layer is "my program has X, I need put put it away somewhere and get it back later". As long as what you get back is what you put, it's OK - no need to worry about the internal details of X or what it might be related to.

An RDBMS is not a persistence layer. No-one from c.d.t has said that it can not be used as a persistence layer. What is often said is that using an RDBMS _merely_ as a persistence layer is a grossly misguided use of machine and human resources.

The relational model is not a great theory of all, it is a logically-based recipe for the long-term management of data. You are the sort of person who degrades it by arguing from a position of ignorance of what it is really about.

>>> I guess that his hidden argument was "because RDB
>>> apparently solves all problems, then data-centric view is the right one."
>> No, the argument is that the data-centric view is often (not necessarily
>> always) the right one to take, and that keeping the data in an RDBMS
>> provides a better basis for solving future problems using the data than
>> any other way of keeping it.
> Ah, that's better. So data-centric view is not universal => then there
> exist cases which cannot be viewed that way => data is not a fundamental
> term => data do not unconditionally exist. Are we in agreement?

No we are not. "cannot be viewed" should be "are not best viewed", and the rest of your implications are nonsense.

>>> Yet another logical fallacy was a data-centric problem statement: "there
>>> will never be any other application that will need my data," used in order
>>> to prove data-centric view itself.
>> There is no fallacy here. First there is a fact - you have data, however
>> you choose to view it. Do you want to deny this?
> Certainly. Non-observable things do not exist. But the fallacy is that you
> are putting existence of data as a fact from which you deduce data
> existence.

I have not deduced data existence from anything, I simply believe it to be a fact.

>>> In OO problems are not modeled in terms
>>> of applications using data.
>> No, but the data is still there.
> In which sense? Laplace has answered this two hundred years ago: "I did not
> need to make such an assumption."

Your quote has insufficient context for me to have any idea what you think it means, or what Laplace thought it meant.

What is your definition of "data"?

E Received on Thu Mar 06 2008 - 15:58:35 CET

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