Dimensional Modeling - Enterprise Data Warehouse Bus Matrix

An Enterprise Data Warehouse (EDW) Bus Matrix is a core planning tool in Kimball’s dimensional modeling methodology that maps business processes to dimensions in a single, unified view of the data warehouse.

Think of it as a blueprint that shows:

1. Rows → Business Processes

   • These are the main activities or events you want to analyze (e.g., Sales Transactions, Inventory Movements, Customer Support Calls).

2. Columns → Conformed Dimensions

   • These are shared reference data tables (e.g., Date, Customer, Product, Location) that have consistent definitions and can be reused across multiple business processes.

3. Cells → Links

   • A checkmark (or dot) in a cell means that business process uses that dimension.

Purpose of the EDW Bus Matrix

• Ensures consistency across the warehouse by enforcing the use of conformed dimensions.

• Helps identify integration points between different subject areas.

• Serves as a roadmap for incremental development of the data warehouse (you can deliver process by process).

• Highlights gaps in data modeling (e.g., missing dimensions or inconsistent keys).

Example (simplified):

Business Process	Date	Customer	Product	Store	Salesperson
Sales Transactions	✔	✔	✔	✔	✔
Inventory Movements	✔		✔	✔
Customer Support Calls	✔	✔			✔

This matrix would tell you, for example, that Customer Support Calls don't track products, but Sales Transactions do — and all use the same Date dimension.

 

The design team scans each row to test whether a candidate dimension is well-defined for the business process and also scans each column to see where a dimension should be conformed across multiple business processes. Besides the technical design considerations, the bus matrix is used as input to prioritize DW/BI projects with business management as teams should implement one row of the matrix at a time. 

The detailed implementation bus matrix is a more granular bus matrix where each business process row has been expanded to show specific fact tables or OLAP cubes. At this level of detail, the precise grain statement and list of facts can be documented.

 

Opportunity/Stakeholder Matrix

After the enterprise data warehouse bus matrix rows have been identified, you can draft a different matrix by replacing the dimension columns with business functions, such as marketing, sales, and finance, and then shading the matrix cells to indicate which business functions are interested in which business process rows. The opportunity/stakeholder matrix helps identify which business groups should be invited to the collaborative design sessions for each process-centric row.