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A subject area is a subset of objects taken from the whole pool of objects in your model. You can create multiple subject areas in your model. Typically, you create a subject area to help you manage a large model, to reduce the number of objects that you work with, or to focus on a particular business function.
Note: If your modeling specifications do not require you to have a subject area in your model, starting with r8, you are no longer required to have at least one subject area for each model. This was a requirement for all models prior to r8.
Working with subject areas is especially useful when designing and maintaining a large or complex data model. By dividing a subject area into several smaller subject areas, you can allow different groups within an organization to concentrate on the processes and tasks pertinent to their own business area.
You create a subject area in the Subject Area Editor, which includes options for selecting the members of a subject area. In the Subject Area Editor, you name the subject area, set global options, and select members to include in the logical model or the physical model, or both. You can also exclude references, during schema generation, to tables that are not in the currently selected subject area. In addition, you can use the Spanning Neighborhood feature to specify how many generations of ancestors or descendants, or both, of the members you select to include in a subject area.
For each subject area that you create, its name is added to the Subject Area list in the Model Explorer. You can switch to a different subject area by selecting it from the list. If you have multiple subject areas in your model, you can create a unique set of diagrams for each subject area. When you switch to a different subject area, you only see the diagram tabs for the current subject area.
When you create a subject area for the logical side of a logical/physical model, a similar subject area is automatically created for the physical side of the model. The reverse of this is also true. If you add or remove members from a subject area, the membership change is reflected in the corresponding physical or logical side of the model but will not affect the membership of any other subject area. If you add or delete objects in one subject area, such as entities and attributes, it does not impact other subject areas.
When you create or edit a subject area, the new subject area or the edits are saved when you close the Subject Area Editor. When you save a model to an .erwin file, the subject areas are saved with the model, not as individual files. When you open a model, all previously created subject areas are available. In a logical/physical model, the logical and physical models share the same subject areas.
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