Re: Peter Chen and Charles Bachman

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.

> That is to say, all the relationships in the data that are
> inherent in the composition of the data, whether it's adjacency,
> navigational, or by common key data, are omitted from this model.

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

> 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.

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