I finally read a book by Inmon (DW 2.0 Inmon et al) and must say I found it very interesting. As a long time adherent to Kimball’s star schema based data warehouse, I must admit to some bias when approaching Inmon’s work. But I did find Inmon’s philosophy gave me pause for thought. Inmon’s critique of the star schema based data warehouse does have valid points. It can be “brittle” as he puts it, resistant to business change. Unfortunately I did not find that he offered an alternative data modeling paradigm, at least not in this book, that would rectify this shortcoming.

Overall, to put it in terms of the proverbial forest and the trees, Kimball’s approach tells you how to properly fell a tree. Inmon’s approach attempts to explain forest management; it is vast and complex, intending to deal with vast and complex data. He describes the four sectors of the data warehouse which are intended to manage data volumes in the most efficient ways possible, based on the statistical likelihood of being called upon. It is difficult to envision this in action, but if it could be done it would be a fast and efficient system.

Kimball’s appeal to me is the simplicity. The star schema approach, like the SQL statement, is a simple concept that can be expanded to include vast complexity. The star schema also fits so perfectly with OLAP modeling it seems like they were made for each other. I think this has led to the wide adoption of the Kimball philosophy.

I have found that business changes can be incorporated easily within a star schema based data warehouse, as long as they are new dimension elements or measures. Difficulty ensues when new fact tables are required, over and over again, especially when granularity becomes an issue. Like an ever expanding puzzle, Kimball’s approach allows additional facts to fit in the model as needed, so additional business requirements can be accommodated. However, if particularly voluminous data, unwieldy data structure or enterprise-wide standard measures across a huge corporation are concerns, Inmon’s approach may certainly be helpful.