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Re: Entity vs. Table

From: Alfredo Novoa <alfredo_at_ncs.es>
Date: Mon, 14 Jun 2004 17:19:50 GMT
Message-ID: <40cdde24.28490266@news.wanadoo.es>


On Mon, 14 Jun 2004 11:05:34 -0400, "Alan" <alan_at_erols.com> wrote:

>I think we are really in agreement, but the use of wrods and relative
>point-of-view is getting in the way. Your view is certainly correct. Much of
>the confusion stems from the use of the term "model", which means different
>things to different people.

I tend to avoid the use of the term "model" and to use design.

>Business Requirements

They are a conceptual design.

>flows to
>Conceptual Design (ERD or other)

Another conceptual design, but you lose a lot of requirements in the transformation. You have to complete the ERD with written rules or anything else.

>flows to
>Logical Design (Mapping to Relational Schema (tables))

A relational design is a logical and formal design.

A good design must include all business rules (integrity and derivation rules).

>flows to
>Physical Design (Indexes, Storage Structures, and other RDBMS-independent
>items)

Do you mean DBMS dependent structures?

Unfortunately with most DBMSs we have very little freedom to chose the storage structures and the physical design is mixed with the logical design.

For instance you have to create an index if you want an alternate key constraint.

Regards
  Alfredo Received on Mon Jun 14 2004 - 12:19:50 CDT

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