Re: OO and relation "impedance mismatch"

From: Gene Wirchenko <genew_at_mail.ocis.net>
Date: Sun, 03 Oct 2004 14:50:03 -0700
Message-ID: <qaq0m0tndbfcokdco7ceiiiephoclshokp_at_4ax.com>


mAsterdam <mAsterdam_at_vrijdag.org> 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?
>
>Nice question.
>
>Maybe an example helps.

[snip]

>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.

     Ah, I was thinking of the database level.

     For the UI, I would find the local and temporary situation fine with reservations:

  1. The database had better not have this inconsistent 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.

Sincerely,

Gene Wirchenko

Computerese Irregular Verb Conjugation:

     I have preferences.
     You have biases.
     He/She has prejudices.
Received on Sun Oct 03 2004 - 23:50:03 CEST

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