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Re: definitions for conceptual, logical, physical

From: Michael Gaab <mike-g_at_montana.com>
Date: Sat, 24 Jun 2006 13:08:03 -0600
Message-ID: <1151175612_23997@sp6iad.superfeed.net>

"Marshall" <marshall.spight_at_gmail.com> wrote in message news:1151082515.490597.297470_at_i40g2000cwc.googlegroups.com...
> Hi all,
>
> We use these terms a lot: conceptual, logical, physical.
>
> I believe I have a good intuitive understanding of these
> terms and how they are used. However, an intuitive
> understanding and a formal definition are not the same
> things!
>
> Anyone have formal definitions for the above terms?
> Citations?

This is far from formal.
Probably just a rehash of what you already know. This is my take.

Conceptual design follows requirements gathering.

Conceptual design models the problem space as the user sees the problem. So all of the terms in this model are terms that the user understands and uses to describe their world.

Logical design.
Make a choice as to how you are going to organize the data: relational, network, hierarchical, flat file, whatever. Map the conceptual model to your choice a logical model using whatever methods that model provides. This model uses language that is independent of any specific implementation.

Physical design.
Map the logical design to the implementation details of the chosen logical model. If you model the data relationally, then you would at this point pick a specific dbms, Oracle, MSSQL, MySQL, etc., but your logical design would map to any dbms.

Mike  

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