Re: OO and relation "impedance mismatch"

From: mAsterdam <mAsterdam_at_vrijdag.org>
Date: Mon, 04 Oct 2004 00:25:13 +0200
Message-ID: <41607c49$0$25965$e4fe514c_at_news.xs4all.nl>


Gene Wirchenko wrote:

> mAsterdam wrote:

>>Gene Wirchenko wrote:
>>>mAsterdam wrote:
>>>>The data in your tables need to be consistent
>>>>with eachother at any point in time. This
>>>>restriction is not necessary at the object
>>>>level and may be perceived more as a hindrance
>>>>than as a feature for the objects. During its
>>>>life the object only needs data necessary for
>>>>its required behaviour.
>>>
>>>     Why is it not necessary for data to be consistent at the object
>>>level?  (Or another way:)  Why is it acceptable for data to be
>>>inconsistent at the object level?

>
>>...In short: I think it is acceptable because the
>>contradictions are local and temporary - but I'ld
>>like to see arguments showing why it should not be.

On second thought: s/because/as long as/

> Ah, I was thinking of the database level.

Ah. Ok. Different system borders. Happens.

>
> For the UI, I would find the local and temporary situation fine
> with reservations:
Why just UI?
>
> 1) The database had better not have this inconsistent data.

Yep. I could imagine situations where
some object could use some non-shared tables with this stuff - but they would not be managed data.

> 2) The inconsistencies must be resolved before the data is written.
>
> It is fine to have invalid data in an input field, but not when
> the input is complete. "-" is acceptable partway input for a number,
> but not for the whole number.
>
> Having debits and credits out of balance is acceptable while one
> is entering them. Otherwise, one would never be able to enter that
> first nonzero value.
>
> This is not the database level though.

Indeed. Received on Mon Oct 04 2004 - 00:25:13 CEST

Original text of this message