Re: Peter Chen and Charles Bachman

From: Leandro Guimarães Faria Corsetti Dutra <leandro_at_dutra.fastmail.fm>
Date: Wed, 05 May 2004 18:36:57 -0300
Message-ID: <pan.2004.05.05.21.36.57.495468@dutra.fastmail.fm>

Em Wed, 05 May 2004 17:02:01 -0400, Laconic2 escreveu:

> Data analysis is much more pervasive than database design. Data can be
> tied back to a conceptual model regardless of whether it is in one
> database or another, or even different kinds of databases, whether it's
> in exchange in the form of XML, CSV, of the responses to SQL SELECT,
> or in forms or reports or wherever.

Useless talk, since none of these gives you a data model as the RM does.

>> An ERD is a diagram.  A draft.  For presentation.  Nothing more.

>
> And ERD is a diagram that represents an ER model. The ER model can be
> more than the diagram.
> But even if it's only the diagram, so what?

It is not a model. It is a draft.

>> 'Common key' is referential integrity, not 'relationships'.

>
> The use of foreign keys to represent relationships is one way to represent
> relationships. There are other ways. For example, in CODASYL, you
> define a set that defines a relationship between the set owner and the set
> members. Referential integrity is merely a mechanism for keeping foreign
> keys from getting orphaned.

Hey, go back to your textbooks. Relationships aren't defined in the RM.

>> So it is not a logical model.  At most a conceptual one, and incomplete
>> at that.

>
> Incomplete for what?

For representing even the most basic constraints.

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Received on Wed May 05 2004 - 16:36:57 CDT