Prior to r8 of erwin Data Modeler, the relationship between Subject Areas, Diagrams and Subject Area member Entities was pretty straightforward. The added flexibility introduced in r8 has left some users migrating from earlier versions a little confused. In this article, I will try to overcome that confusion.
In r7 and previous versions, a diagram was:
- known as a Stored Display
- always attached to a Subject Area and a Subject Area had to have at least one Diagram
- automatically populated with all Subject Area member Entities/Tables (with an option to display or hide database Views)
In addition, there was always a Subject Area called <Main Subject Area> which contained all Entities/Tables within the Model, so by implication, there was always a Diagram which contained all Entities/Tables within the Model.
In r8 and beyond, a diagram:
- is now known as a Diagram
- may be related to either a Subject Area or the Model
- may contain any number of Entities/Tables from its owning context (Model or Subject Area)
- is initially created with no members (except for models created by conversion, import or reverse-engineering)
- must be populated through the drawing pane or the Diagram Editor
- may be “Auto Populated” with all members of its context
- has a new Members tab in the Diagram Editor, similar to that in the Subject Area Editor
There is no longer a <Main Subject Area>.
When you create a new Model, a new Model-level Diagram will be created automatically, and similarly, when you create a new Subject Area, a new Subject Area-level Diagram will be created.
If you want a Model-level diagram to behave like a r7 <Main Subject Area> Stored Display, then check the Auto-populate option in the Diagram Editor.
Alternatively, you can create a Subject Area, name it <Main Subject Area>, select the Auto-populate option in the Subject Area Editor and select the Auto-populate option in the Diagram Editor for the associated Diagram to carry on working in the way you did with r7.