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Neil Raden

I hope that you will engage with me with your comments as we explore the future of business intelligence (BI), particularly its expanding role in the actual process of making decisions and running an organization. BI is poised for a great leap forward, but that will leave a lot of people and solutions behind so expect a bumpy ride. I also expect there will be a flurry of advice and methodologies for moving BI into a more active role, one that will widen the audience as BI meets more needs. But a lot of that advice will be thin and gratuitous, so hold on while we put it under the microscope. You can reach me directly if you prefer at nraden@hiredbrains.com.

About the author >

Neil Raden is an "industry influencer" – followed by technology providers, consultants and even industry analysts. His skill at devising information assets and decision services from mountains of data is the result of thirty years of intensive work. He is the founder of Hired Brains, a provider of consulting and implementation services in business intelligence and analytics to many Global 2000 companies. He began his career as a casualty actuary with AIG in New York before moving into predictive modeling services, software engineering and consulting, with experience in delivering environments for decision making in fields as diverse as health care to nuclear waste management to cosmetics marketing and many others in between. He is the co-author of the book Smart (Enough) Systems and is widely published in magazines and online media. He can be reached at nraden@hiredbrains.com.

Recently in Federated Data Warehouse Category

Bill Inmon posted an article  where he discussed the drawbacks of a "virtual data warehosue." Now the idea of a virtual data warehouse has been around for years (I remember IBI positioning their EDASQL technology as a virtual data warehouse fifteen years ago). That was a terrible idea then because it provided only a method to access data, with no proper cleansing, integration or persistent storage of it. It was, frankly, not a data warehouse at all. Using that definition, anyone would agree that a "virtual data warehouse" was not a workable solution.

The problem is that Inmon defines any method to augment the data warehouse with access to source data directly as a virtual data warehouse, and in the same terms as the IBI concept from long ago, citing its shortcomings, casting the virtual data warehouse as not only a bad idea, but one that has been historically bad and discredited. In fact, the term "virtual data warehouse" has been used for years by detractors for any idea that augmented or supplemented the data warehouse architecture, many of which were truly misguided ideas. In today's world, though, it is not only possible, it is necessary to supplement the data warehouse. This "virtual data warehouse" is a new thing, something not possible before.

Inmon's primary argument about virtual data warehousing is that it skips the crucial step of integrating data:

The great appeal of the virtual data warehouse is that you do not have to face the problem of integration. 

This is the central premise of his argument, that a virtual data warehouse skips data integration.  What actually happens in today's version of a virtual data warehouse (and it shouldn't really be called that) is that a central data warehouse endures, with the kind of integrated data that Inmon would approve of. However, since there are so many data sources now, they change more frequently and the volumes are extreme, the batch load data warehouse is burdened with latency and often impractical for 100% of the analytical requirements. Because system architecture has changed so radically over 15 years, it is possible to read logs, queues, perform changed data capture and even go directly into the operational systems without resorting to extraction into staging areas or degrading their performance. The semantics of these source systems are considerably more transparent than they used to be and the speed of processing is so much faster it is possible to cleanse and integrate data on the fly. In those cases where it is not feasible, or where for a myriad of reasons it makes sense to warehouse the data, that process is preserved. So the virtual data warehouse is actually more of a surround strategy than an alternative. 

Why then is the virtual data warehouse such a supremely bad idea? There are actually lots of reasons for the vacuity of virtue manifested by the virtual data warehouse. 

I won't repeat all of his reasons, but they all seem to be related to the old "it will bring the system to its knees" claims about the inefficiency of federated queries and the affect on systems and network performance. I call this reasoning "managing from scarcity," except there is no scarcity anymore. Again, not every query is federated; many will be satisfied by the data warehouse. We can build systems thousands of times larger and millions of times faster than we could two decades ago as data warehousing was catching on and isolation of data and processing was absolutely necessary. Today's applications and business processes call for faster, fresher data than a data warehouse can provide, in many cases. Rather than ignore these requirements, a virtual data warehouse (with adequate semantic rationalization) gives the developers a chance to position the processing to the logical location, and the ability to use abstraction (or indirection if you prefer that word) to address the data, providing the flexibility to change that configuration whenever necessary. 

The ugly truth is that the corporate analyst MUST do integration whether he or she wants to or not. There is no getting around it. Wishful thinking just does not cut it here.

Who wouldn't agree with that? The question is, where and when? The bulk of the difficult integration work is manual - people gathering information and getting buy-in that they have the right mapping. Where that process gets implemented is not the issue. There is no rule that says it must all go to a data warehouse. Historically, that was the practice because of the constraint of resource limitations that are now mostly relaxed.

So the problems with the virtual data warehouse are legion. There is poor performance or no performance at all. There is an enormous system overhead. There is only a limited amount of historical data. There is the work of integration that each analyst must do, one way or the other. There is no reconcilability of data. There is no single version of the truth for the corporation.

All of these things are true in the virtual data warehouse the way Inmon defines it, a big mess of federated queries directly to source systems with no integration, no history, no real context. No one would suggest this is a good idea. But a data warehouse today should be a participant in a constellation of source data, so long as the access methods to data beyond the warehouse's control can be relied upon to be correct, timely and not a burden on other systems. This kind of arrangement is not a virtual data warehouse, it's an analytical framework. We should discuss the merits of the idea as such, not dismiss them because we name them with a long-discredited concept. 


Posted March 23, 2009 2:24 PM
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