A student attending one of Kimball Group’s recent onsite dimensional modeling classes asked me for a list of “Kimball’s Commandments” for dimensional modeling. We’ll refrain from using religious terminology, but let’s just say the following are not-to-be-broken rules together with less stringent rule-of-thumb recommendations. Rule #1: Load detailed atomic data into dimensional structures. Dimensional models […]

Successful data warehouse and business intelligence solutions provide value by helping the business identify opportunities or address challenges. Obviously, it’s risky business for the DW/BI team to attempt delivering on this promise without understanding the business and its requirements. This Design Tip covers basic guidelines for effectively determining the business’s wants and needs. First, start by properly preparing […]

Students often blur the concepts of snowflakes, outriggers, and bridges. In this Design Tip, I’ll try to reduce the confusion surrounding these embellishments to the standard dimensional model. When a dimension table is snowflaked, the redundant many-to-one attributes are removed into separate dimension tables. For example, instead of collapsing hierarchical rollups such as brand and category into columns […]

Many transaction processing systems consist of a transaction header “parent” with multiple line item “children.” Regardless of your industry, you can probably identify source systems in your organization with this basic structure. When it’s time to model this data for DW/BI, many designers merely reproduce these familiar operational header and line constructs in the dimensional world. In this Design […]

With the current industry buzz focused on master data management (MDM), it’s time to revisit one of the most critical elements of the Kimball method. Back in 1999, Ralph Kimball wrote an Intelligent Enterprise column entitled The Matrix. The 1999 movie of the same name spawned two sequels, but we haven’t devoted a column to […]

How do you deal with changing dimensions? Hybrid approaches fill gaps left by the three fundamental techniques. Unlike most OLTP systems, a major objective of a data warehouse is to track history. So, accounting for change is one of the analyst’s most important responsibilities. A sales force region reassignment is a good example of a […]

Do you know the difference between dimensional modeling truth and fiction? According to Merriam-Webster, fables are fictitious statements. Unfortunately, fables about dimensional modeling circulate throughout our industry. These false claims and assertions are a distraction, especially if you’re trying to align a team. In this column, we’ll describe the root misunderstandings that perpetuate these myths so […]

The Kimball bus architecture and the Corporate Information Factory: What are the fundamental differences? Based on recent inquiries, many of you are in the midst of architecting (or rearchitecting) your data warehouse. There’s no dispute that planning your data warehouse from an enterprise perspective is a good idea, but do you need an enterprise data […]

I worked at a company called Metaphor back in the early 1980s. As part of a startup software company introducing then-cutting-edge concepts (such as folders, file drawers, and workflows on a graphical electronic desktop), I appreciated the benefits of using metaphors to represent seemingly complex concepts. Effective verbal and visual metaphors are able to convert complexity into […]

People often engage us to conduct dimensional model design reviews. In this column, I’ll provide a laundry list of common design flaws to scout for when performing a review. I encourage you to use this list to critically review your own draft schemas in search of potential improvements. What’s the Grain? When a data warehouse team […]