Kimball vs. Inmon: You Want the Truth?!
Ralph Kimball and Bill Inmon have long fought over the title of Father of Data Warehousing. For Kimball, it is a title that has been bestowed upon him by his peers, but some say Inmon's title is self-appointed. Regardless, both men have brought a great deal to the world of data warehousing, establishing the structure and frameworks that we still use today. When building a data warehouse, people will either say we took the "Kimbalistic approach" or we took the "Inmonistic approach." Right here, right nowwe will define, once and for all, what is meant by each approach.
The Kimball approach is an iterative approach where the data warehouse is built one piece at a time. Kimball identifies common (shared) dimensions within the data warehouse (i.e. customer, time, geography) that will be used across multiple fact groups (i.e. purchase history, billing history) at a high level. He then suggests that we should build this data warehouse one fact group at a time. Kimball calls each of these a "data mart." By developing all of the data marts and populating the shared dimensions, the data warehouse is built. Kimball's approach is definitely a bottom-approach where the warehouse is built piece by piece with a higher level framework in mind. In the Kimball methodology, it is important to remember that the data mart is simply a piece of the larger
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