Kimball Bus Matrix

1. What Is the Kimball Bus Matrix

The Kimball Bus Matrix is a planning and governance artifact used in Kimball Dimensional Architecture. It defines how business processes relate to conformed dimensions across the enterprise.

It serves as the architectural blueprint for building a scalable, integrated dimensional data warehouse.

2. Visual Example of a Kimball Bus Matrix

3. Structure of the Bus Matrix

3.1 Rows: Business Processes

• Each row represents a business process
• Each process typically maps to one fact table

• Sales
• Orders
• Shipments
• Inventory
• Returns

3.2 Columns: Conformed Dimensions

• Each column represents a shared dimension
• Used consistently across multiple fact tables

• Date
• Product
• Customer
• Store
• Promotion

3.3 Intersections

• An X indicates the dimension is used by that process
• Defines required dimension keys for each fact table

4. Textual Representation of a Bus Matrix

Business Process | Date | Product | Customer | Store | Promotion
---------------------------------------------------------------
Sales            |  X   |   X     |    X     |   X   |     X
Orders           |  X   |   X     |    X     |   X   |
Shipments        |  X   |   X     |          |   X   |
Inventory        |  X   |   X     |          |   X   |
Returns          |  X   |   X     |    X     |   X   |

5. Why the Bus Matrix Is Critical

• Prevents data mart silos
• Enforces conformed dimensions
• Ensures enterprise-wide consistency
• Supports incremental development
• Acts as a long-term architecture contract

6. How It Drives Dimensional Design

1. Select a business process (row)
2. Declare the grain of the fact table
3. Attach all marked conformed dimensions
4. Design the star schema

7. Relationship to Kimball Architecture

• Each row becomes a fact table
• Each column becomes a dimension table
• The full matrix forms the enterprise data warehouse

8. One-Sentence Summary

The Kimball Bus Matrix defines which conformed dimensions apply to each business process, ensuring scalable, consistent, and integrated dimensional analytics.