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Re: Indexes and Logical design

From: vldm10 <vldm10_at_yahoo.com>
Date: 16 Sep 2005 17:01:34 -0700
Message-ID: <1126914599.720399.92340@g47g2000cwa.googlegroups.com>

> Maybe the best distinction (in the terminology) is the one Data Architect
> makes: between "Schema Objects" and "Database Objects". But I'm not sure.

Say that you have a schema in the RM, and let this schema hold true in one particular database. As the database (data) changes with time, this schema holds true in all these databases. Besides having some simple language L, the schema can have some constrains. Let us call the database "a good one" if the constraints are satisfied in the database. Briefly a database is a model for a schema. Say that now somebody else designs an OO schema and let this schema hold true in the
OO databases with same data. If there is a correct mapping (or maybe morphism) between mentioned RM schema and the OO schema, then I believe that we have something which we can call Janus with two faces, but one Conceptual Model.

> This opens a whole other subject. If a database gets "denormalized" in the
> course of implementation, perhaps its good to keep a copy of original
> normalized model around, and in synch with whatever alterations get made to
> the implementation. That way, someone who wants a REAL logical view of the
> relations can get such a view without the obstructions imposed by SQL and by
> real world considerations. Is it worth the cost? I don't know.

Vladimir Odrljin Received on Fri Sep 16 2005 - 19:01:34 CDT

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