Re: Mixing OO and DB

From: Dmitry A. Kazakov <mailbox_at_dmitry-kazakov.de>
Date: Thu, 14 Feb 2008 11:47:29 +0100
Message-ID: <4aqww9ym31zj.c8np5b06w4pm$.dlg_at_40tude.net>

On Thu, 14 Feb 2008 01:14:13 +0100, mAsterdam wrote:

> Dmitry, why are you engaging in this thread?

Don't know, probably it was my mistake. I hoped that there could be some civilized exchange of meanings rather than usual cursing and calling others idiots.

>>>> But why is recording essential? 
>>> To facilitate the sharing of observations.
>> 
>> So, we have now:
>> 
>> 1. observations
>> 2. entities (busy with sharing observations)
>> 3. actions (state?) of sharing something (like observations)
>> 4. identity (of "same" thing being shared/observed)
>> 5. identity (of "different" entities observing "same" thing)

>
> No we don't. You don't have anything here, because you reject the
> existence of data. Beyond some agreement on that any attempt at
> formalization of it is futile. You asked my opinion, you reflected it
> against some of your preconceptions about what to formalize
> and what not, and something comes out.

But you certainly should have a mental picture where "data" plays some role. Let you to tried to formalize it. You would describe some properties and axioms about "data". You would also like to remove much of unnecessary and uncertain things (like 1-5 from there). What I tried to say is that after doing this, you could probably notice that you can remove "data" from your system without any loss...

> Which primitive elements does your formal system have?

Value, type, variable, operation.  

>> Bad. It means that you have to formalize "memorize" in some quite tricky
>> way. Honestly I don't know what could be the difference between "memorized
>> Pi", "not-yet-memorized Pi", "once-memorized-but-forgotten-by-now Pi" and
>> so on.

>
> Are you suggesting π is data?

Yes. But you can take some P(pi)=true instead.

>>>> May I translate data into a different
>>>> representation and then erase the original record? 
>>>> Will data still be there?
>>> Iff it conveys the same facts as the original record, sure.
>> 
>> OK, that means that data = facts + record medium of:
>> 
>> D = (F, R)

>
> Guessing about your notation as D denotes Data, F denotes Facts, R is
> the requirement that the fact is recorded, R is just 1.

(A side question, in "R is just 1", were "just 1" data or fact?)

>> It also states that
>> 
>> F1 = F2 => D1 = D2

>
> Almost. Within a shared set of observations,
>
> F₁=F₂ ⇔ D₁=D₂

Even stronger, also.

>> Why should I care about R, then? 

>
> Why do you? I don't yet.

I order to get rid of it. (It is not only for the sake of reducing the system. It is also in order to describe R in terms of the formal system. We want to be able to implement DBMS, don't we? So we need a formal system where R would be formalized.)

> For now, I don't care about its internals,
> just that it exists so we have a way to record facts.

If you have an equivalence of facts and data, then you need some additional means in order to distinguish them. And, equivalently, you cannot describe recording in terms of either data or facts.

>> Pi is Pi and retains all its property
>> independently on where and how you write it (or not). Let's declare F = D
>> and forget about R.

>
> For now - ok.
>

>> (BTW, some of DB people regularly posting to comp.object vehemently denied
>> that DB is about persistency. Could you clarify it?)

>
> No, not at this point. This is best left to a thread on its own.
>
> Disclosure: I have in the past vehemently denied that DB is about
> persistency, and I have yet to see a coherent argument that
> it would be. Assume for now it is a belief I turned to
> after experiencing the way the smalltalk system image works and
> Rumbaugh's remarks on persistency.
>

>>>> A formal system operates on data
>>>> without any clue of the meaning of.
>>> I think that is to crude.
>>> The meaning itself is informal, hence inherently impossible to fully
>>> access from within the formal system (I think we agree on that).
>>> However, without meaning to associate it with, a formalism is useless.
>> 
>> It is a tautology. You say that without meaning there is no meaning. 

>
> No, though your rephrase is (a tautology).
> I'll state it differently.
>
> Without shared, informal denotations, any formalism is useless crap.
> I don't want it and you don't want it.

This is not the same as meaning, and uselessness is yet another thing. But I see no disagreement in the core issue: a formal system does not operate meanings. It is we who assign meanings to the inputs and outputs, and, at yet another level of understanding, judge about the formal system as a whole in terms of its usefulness, for example.

>> Yes, we cannot reason about meaning while staying 
>> within the same formal system.
>> Because you seem to bind data with a meaning (as I do), that immediately
>> kicks the notion of data out of the formal system. So data do not exist
>> there. Which is all my point! No data, nothing to worry about.

>
> And the result is a hermetic system as useful as solipsism.
> Have some fun there! I'm out waiting until you are bored of it.

OK, I am back on vacation. How are you going to formalize something which cannot be formalized? (:-))

-- 
Regards,
Dmitry A. Kazakov
http://www.dmitry-kazakov.de

Received on Thu Feb 14 2008 - 11:47:29 CET