Subject Area* — A coherent, mind-sized portion of the Common Data Model organised around one Root Entity Type and used to understand and validate a specific L3 capability.

A Subject Area brings together the Entity Types, relationships, rules and relevant business context needed to understand a manageable part of the Common Data Model.

Each Subject Area belongs to one L3 capability and has one Root Entity Type. The Root Entity Type provides the main focus for the Subject Area. Other Entity Types are included only where they are needed to understand or validate that capability.

For example, in the L3 capability Product Order Management, ORDER may be the Root Entity Type. ORDER LINE is part of the Order structure, while CUSTOMER and PRODUCT may appear as peripheral Entity Types because their relationships to the Order matter. Their own internal models remain governed elsewhere.

Subject Areas allow detailed modelling and Gemba validation to proceed in portions small enough for people to understand and challenge while remaining connected to the enterprise-wide Common Data Model.

A Subject Area is not a separate data model. It is a focused view of the Common Data Model for human understanding and validation.

Related glossary items:

• 📝 Common Data Model
• 📝Business Object

For more information, see:

Subject Area: Enterprise Architecture — Foundation of Shared Knowledge

*Note: Not to be confused with a category of document on this site; also a Subject Area