Re: Peter Chen and Charles Bachman

Leandro Guimarães Faria Corsetti Dutra <leandro_at_dutra.fastmail.fm> wrote:

>Em Wed, 05 May 2004 15:06:11 -0400, Laconic2 escreveu:
>
>> an ER model is a "data model" but it is not a "database
>> model".
>
> Hair splitting.
>
> An ERD is a diagram. A draft. For presentation. Nothing
>more.

     Bah! You think I am going to go to the trouble of drawing something useless? If I have an ERD, I use it to develop the database schema.

[snip]

>> That means that once you have an ER model that is satisfactory to both the
>> SMEs and the designers, you are still free to choose an implementation,
>> without having to "undo" decisions made in the ER model. As has been
>> said before in this forum, it's the difference between analysis and
>> design.
>
> So it is not a logical model. At most a conceptual one, and
>incomplete at that.

     Nope. It can be a logical model, if done to a RW amount of detail. It is not the physical model though.

Sincerely,

Gene Wirchenko

Computerese Irregular Verb Conjugation:

     I have preferences.
     You have biases.
     He/She has prejudices.