Sunday, February 12, 2012

Death of the Star Schema?

by Tom Gleeson of Gobán Saor

With the release of the next version of PowerPivot (Microsoft) around the corner (mid March I think), I’ve been re-acquainting myself with its new features. Most of the current version’s annoyances have been remedied (no drill-thru, no hierarchy support for example); and the additional enhancements to the DAX language (crossjoins, alternate relationships etc) make modeling most any problem possible (and generally easy).

Death of a Star

The more I come to know PowerPivot, the more I believe that modeled data warehouses' days are numbered. I didn’t say data warehouses per se, rather those that attempt to centrally model end user reporting structures (usually as star-schemas).

There will continue to be a need for centrally controlled data warehouses (or at least simplified data views (and/or copies) of operational datasets, either provided by system vendors of by in-house IT) to bridge the raw-to-actionable data gap. But I suspect the emphasis will change from providing finished goods to providing semi-processed raw materials.

So, will the star-schema become redundant? No, as it’s still a valid method of modelling a reporting requirement in order to make many queries simpler to phrase (this obviously applies to SQL , but also to DAX queries). But, those who build them will be doing so closer to the problem at hand, and specific to that problem (I’ve discussed this before in Slowly Changing Dimensions: Time to Stop Worrying).

For many reports the barely modified operational data model will be all that’s required (for example, DAX doesn’t require “fact” header/detail tables to be flattened to detail level, as would be the case with a classic star).

“Good Enough” models will become the norm; classic “Everything You Ever Wanted to Know” centralised models a luxury for most (especially as such models tend to “age” very quickly).

If you’re about to invest or re-furbish your data warehouse or your reporting data sub-systems, don’t do so without first taking a serious look at PowerPivot. This is a game-changer, not just for full-stack Microsoft BI shops, but for any business that finds that their reporting datasets invariably end-up in Excel.

If you need any help evaluating PowerPivot or modeling your reporting needs in PowerPivot, I’m for hire.

Source: Gleeson, T (2012, January 19), Death of the Star Schema? Gobán Saor.

Republished with kind permission of Tom Gleeson of Gobán Saor

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