Kimball

Kimball refers to Ralph Kimball and his data warehouse design methodology, described in The Data Warehouse Toolkit (first edition 1996, third edition 2013).

The approach #

The Kimball methodology rests on three pillars:

• Dimensional modeling: organizing data into star schemas with fact tables and dimension tables, optimized for analytical queries
• Bottom-up: building the DWH starting from individual departmental data marts, progressively integrating them through conformed dimensions
• Bus architecture: a framework for ensuring consistency across data marts through shared dimensions and facts

Slowly Changing Dimensions #

Kimball defined the SCD (Slowly Changing Dimension) classification into types 0 through 7, which has become the de facto industry standard. Type 2 — with surrogate keys and validity dates — is the most widely used for tracking dimension history.

Kimball vs Inmon #

The main alternative is Bill Inmon’s methodology, which proposes a top-down approach with a normalized (3NF) enterprise data warehouse from which data marts are derived. The two methodologies are not mutually exclusive and many real-world projects adopt elements of both.