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Message Posted: Mon, 11 Nov 2002 @ 21:14:06 GMT

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Subj:   Re: 3NF vs Dimensional modelling
From:   McBride, Michael

  Mike Buckland - "However it's just easier to get there if you start with a dimensional model."  

I started to get rug burns from rolling on the floor and laughing so hard at that one. Once I gained my composure, I decided to be as polite as I could muster. Regardless, it isn't easier, it is just cheaper, quicker, faster, to compromise stable corporate data assets, than it is to achieve a long-term, lasting "value" in the core data warehouse.

What I have not said up to now, but I believe to be the case, is that DM (stars, flakes, etc) fill a powerful niche in the datamart portion of a total EDW solution. And, it suffices for the one-subject data warehouse, on its own merits. But if the emphasis is only on reporting and analysis, then the dw will undergo constant change and redsign, when more and more subject matter requirements are placed on that paradigm. That, to me, is never "easy". It is costly, and frought with frustration and peril (what happens if you break the original functionality?).

NF works better in an Enterprise environment where multiple incongruous subject matter must be merged and married in a rational, functional fashion. The DW must have the fleixability to evolve over a long period of time, if the client is going to maximize the investment and more importantly 'realize' a return on that investment. In order to evolve with the least turmoil and aggitation and at minimal developmental expense, NF beats DM hands down.

Put the datacore in NF and leave it alone, put the analysis stuff in a DM datamart, sourced from the EDW, and let it change as needed, add more functionality at the core, and the bring the datamarts up to speed as required (if there even needed). You end up with a win-win for the entire project and the future stability of the organizations DW remains intact, and you protect the original investment.

Unless, of course, you have some other ulterior motive for not wanting your corporate assets as stable, flexible and reliable as possible?

Michael McBride

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