Mastering Data Warehouse Design: Relational and Dimensional Techniques [Paperback]

 

 

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If you want to build a Corporate Information Factory (CIF) I suppose this book is better than many of the previous attempts at teaching how to accomplish that goal. However, like many of the previous Inmon/Imhoff books, there is too much theory (unfocused at that) and not nearly enough practical/tactical content. If you are on the CIF bandwagon however, you will find the book very helpful as compared to most of the previous books on the topic.

But that begs the question. Many a CIF or enterprise-wide project has been launched... yet most are cancelled long before reaching the finish line. This is reality. In the REAL world we have REAL deadlines and REAL budgets imposed by REAL business executives who have REAL problems to solve and it involves... oh by the way... REAL MONEY!

We have to deliver NOW! Well, ok, maybe not quite that fast, but you get the idea. The hard part is getting the data! Or is it? Using simple tools and a powerfully designed, highly detailed dimensional database, we have, for example, clients pulling their own data sets ready for import into statistical and mining packages. They think they have died and gone to heaven!

Foist a third normal form (3NF) design on them and their eyes roll... "Now, which of the available join paths is the right one for this business question?" and "Why is it taking so long for the query?" and "Will you pull the data for me?" Now we hear... "Instead of spending 80% or 90% of my time getting the data prepared, I spend 5% or 10% of my time doing that... so I have that much more time to actually think about the business." We have seen clients' ability to understand and drive their business expand beyond their own wildest imagination in very short order. It shows on their bottom line and they are very happy with that!

The whole point of BI - beyond all the data capture and cleaning and integrating and turning "data into knowledge", and making it easy for the user without dumbing it down, and all that stuff - the point of BI can be distilled down to one word: "Publish!" Booksellers don't hand you a photocopy of a handwritten manuscript. They do a lot of work with the "raw data" - typesetting and page numbers and table of contents and indexing and so on - and turn it into something accessible and useable... something we call a book. That's the point of BI. This book doesn't get it.

Too many CIF or "enterprise" projects have imploded under their own weight to slavishly duplicate the same mistakes. Too many dimensional systems have succeeded with huge return on investment to relegate the ideas to a dark corner.

If we stop the religious discussions (Mac vs. Windows, or the "Inmonites vs the Kimballites") and get to see how truly successful Business Intelligence (BI) systems work, we find the emphasis must be on using proper theory (not arguing it) and applying techniques that work NOW. More often than not, can you say "Dimensional!" Yes, CIF and all that has its place... but not nearly to the degree that this book would have you believe. The most successful clients have been the ones who bypassed all the "modeling wars" and used the data bus architecture of conformed dimensions. They didn't pick and chose a modeling idea or two; they actually studied Kimball and did it the right way. Dr. Codd, while addressing this question one day, asked me this question: "Would you run an OLTP system against a dimensional model?" My obvious answer was: "Of course not." "Why then," he asked, "do so many people try to do the opposite?"

The biggest "problem" with the dimensional approach is that people who do not truly understand it try to pick and chose techniques from it and graft those into their current ways... and fail... and bash it. Or, they don't understand it at all. Uh, sorry, it isn't the technique that is the problem.

The book purports to "answer" a message reply that Ralph Kimball posted on a discussion board some time ago. It does not. One can be certain that Ralph Kimball did not give permission to use his name on or in the book, as is done. Instead, the book does a very poor job of showing how to design and use dimensionally designed databases as a part of a larger architecture, illustrates a complete lack of understanding of the underlying principles, and then criticizes and limits the technique and its application. This does a terrible disservice to the reader... especially a reader who is trying to decide how to meet a real business need and is new to BI. I dislike speaking impolitely like this, but the truth is more important in this context. Also, on the back cover, they state that Ralph Kimball's "letter" was a challenge. It was not. It was merely a listing of many of the crucial issues in a useful BI environment addressed to an individual who had asked legitimate questions about BI. As for addressing these issues "head-on", the book does not do this at all.

Does this matter?

Of course it does. Real people buy this book and are led down a path that rarely leads to success. I realize that much of this review is not directly about specific details of the book. The details in the book are inconsistent, often unfocused, and sometimes downright misleading. The larger issue, and thus the focus of this review, is that the entire book is based on a premise that the CIF is "The Way" and that dependent dimensional data marts are grudgingly "ok". This is not the reality that many of us see in the business and education worlds.

The ability of the author's to communicate is about the worst I've come across. Anything by Kimball is more understandable and readable. Also, by way of comparison, Ken Henderson, of SQL Server Guru fame, knows how to write. These people don't. The lack of practical application is striking, and you will not "Master Data Warehouse Design". Any concept introduced is never exemplified, and the amount of contradictory statements is off the charts. Note how I've failed to show examples from the book to back up my statements, well, they're entire book is like that. Do yourself a favor and read Kimball's texts, at least he can communicate.

A few random comments....
•The back cover says it "addresses head-on" the issues from Ralph's famous letter. I'm familiar with that letter. Either I skimmed over a couple pages too fast - and those pages had some "answer" buried in them, or, they did not really, fully, address many of the issues Ralph wrote about.
•I kept getting confused - some times the book acted like it loved a synergy and partnership between the normalized and the dimensional approaches. Other it seemed to slam the dimensional approach as not working in many areas. In particular, I was shocked at the paragraph in the center of page 386. I've had no problem, using what may appear to be unrelated star schema data, in doing significant analysis and data mining.
•The paragraph on page 394, under "Flexibility", says I can't do sophisticated or advanced analytics from my star schemas. I have. What am I (or, the authors) missing?
•Chapter 6 - Modeling the Calendar... I feel for anyone new to this arena trying to decipher the information. I have no problems with my date or time dimensions and I can explain them to my students in a lot less time than it took me to read that chapter!
•Chapter 7 - Modeling Hierarchies... Seemed a little long. I should not comment on it - when I finished reading it, I realized I had been sleeping through most of it.
•I found the chart on page 100 a little scary - do they really mix the facts in a fact table? The chart shows sales and sales objectives in the same fact table. Is this just a "logical" star? Or, is their basic understanding of the dimensional model in need of an upgrade?
•Not enough real world "how-to" examples.
•Again, either I skimmed a few pages, or, they refer to "we'll address this in a later chapter" a few times and never did.
•I don't know the authors - did not have any pre-conceived opinions about them. Now, I felt like, as a team, they did not always agree on what to write, so they compromised - picked middle ground and sent inconsistent messages. I finished the book with a very unclear picture of what message they were sending.
•Too much extraneous data in many of the examples - tough to weed out the needed from the excess...
•I won't argue with the overall concept of a staging area/data warehouse/data mart philosophy. I do take exception to the inference that I cannot be successful if I don't follow it. I've implemented using that model and variations of the approach, as well as taking real-time transactional data directly into a star.
Final thought. In my experience, anyone taking this book as an "absolute" will spend more time on I/T "stuff" than the users I know will want to put up with. Fifty-some years ago, Aritotle Onasis said the secret of business is in knowing something that no one else knows. That is no longer a reality. This is called the "information age" for a reason. The winners are those that realize they know no more than their competition, but do more, faster, with what they have. In my version of the "real world", executives want results, NOW. I did not feel the authors ever had to deal with "urgency".

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4.0 out of 5 stars A hint toward a real design
A description of data warehouse issues well balanced between business orientation and technical/scientific principles and problems is a very difficult task. Read more

Published on April 21 2004 by Massimiliano Celaschi

1.0 out of 5 stars Dimensional modeling misinformation
This book claims to "be a cutting-edge response to Ralph Kimball's challenge to the data warehouse community that answers some tough questions about the effectiveness of the... Read more

Published on Mar 5 2004 by Mario Di Giovanni

5.0 out of 5 stars Excellent Resource for all Data Warehouse Developers
This is an excellent book for all Data Warehouse Designers and Devleopers. The book makes the Corporate Information Factory a reality and provides the details to build the... Read more

Published on Feb 7 2004 by Edward Martin

5.0 out of 5 stars Integration Of Inmon & Kimball Thinking
"Mastering Data Warehouse Design" is an excellent book to help readers understand how to take maximum advantage of the strengths of diverse approaches associated with... Read more

Published on Oct 29 2003 by Doug Buchanan

5.0 out of 5 stars A top class encyclopedia!
An excellent compendium of Data Warehousing, Modeling, and Management processes. It is a detailed practical-guide for IT implementers and a terrific framework for Architectes to... Read more

Published on Oct 17 2003 by rajeevrawat

5.0 out of 5 stars All in one Guide, Text-Book, and handy Reference
Experienced and new to DW-BI professionals will find this work useful. It shows how to cure the ills from past systems and streamlie going forward. Read more

Published on Oct 17 2003 by rajeevrawat

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