Re: Peter Chen and Charles Bachman

"Leandro Guimarães Faria Corsetti Dutra" > > an ER model is a "data model" but it is not a "database
> > model".
>
> Hair splitting.
>

No, no, a thousand times NO!

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.

In particular, an enterprise could commit itself to a single conceptual model, for all data other than encapsulated data. And it could adhere to this model even if it continued to use products that don't talk to each other.

> 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?
>
> '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.

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

Incomplete for what? Received on Wed May 05 2004 - 23:02:01 CEST