Mastering Data Warehouse Design: Relational and Dimensional Techniques [Englisch] [Taschenbuch]

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.