DBMS, October 1997
An ER Visit
I very much enjoy reading Ralph Kimball's various articles. In his August 1997 article, "A Dimensional Modeling Manifesto", I got the impression that the entity-relation (ER) diagram was no longer useful and had been replaced by the dimensional-modeling (DM) diagram. I thought that ER diagrams helped enforce data integrity for OLTP systems. Especially ER diagrams that enforce third through fifth normal forms. Would it be acceptable to conclude that ER diagrams have their place in OLTP and can be a complementary discipline to DM diagramming?
I definitely have quite a bit to learn about DM since I have been a relational modeler for more than six years. Guess you could say that I'm ER-biased!
Randy Kennedy
rkennedy@us.oracle.com
Thank you for your comments. I do not recommend that the ER design methodology be abandoned in favor of dimensional modeling (DM). Rather, the powerful ER techniques for reducing
redundancy and enforcing low-level data rules should be used where they are appropriate--namely for designing OLTP systems where the emphasis is on updating the data. A well-designed OLTP system can then be a perfect feed for a data warehouse. Dimensional modeling, rather than ER, should be used for designing systems for querying. A modern data modeler (who has responsibilities for both OLTP systems and data warehouses) needs to understand both ER and DM techniques and use them in separate
applications.
--Ralph Kimball
Joe Boggles the Mind
Every article by Joe Celko is not only mind boggling and informative, but also humorous. Sometimes I
wonder what it would be like to think like him. The last line of the answer to his quiz in his July 1997 DBMS column was a howler.
May I add that the other authors are very good. Phenomenal! Of course, only Joe can give you a blend of a twist of the brain and a laugh at the same time.
Cecil D'Souza
cecil@total.net
Help Found
I couldn't help but notice the "Help Wanted" ad in Nelson King's July 1997 article, "Object DBMS's: Now or Never." Nelson writes that "Object-oriented database management could use a high-profile champion, but the realities are that revenue estimates for the ODBMS vendors are under $50 million even for the largest (Object Design Inc.), and all of them together have less revenue than Oracle spends on advertising."
CA is that champion with total revenues of over $4 billion. CA has taken the counter approach to the other major relational database vendors in coming out with Jasmine --a pure object-oriented DBMS and multimedia application development platform developed in partnership with Fujitsu Ltd. We tried extending CA-OpenIngres, our own robust RDBMS and found out early in the R&D cycle that performance and flexibility suffered. CA learned the lesson from our own R&D that trying to extend relational databases just doesn't work. For today's multimedia database needs, we clearly see pure object technology as the way to go.
Dustin McNabb
Computer Associates International Inc.
mcndu01@cai.com
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Updated September 17, 1997