Transforms › Role of Transforms in Supertype-Subtype Relationship

Role of Transforms in Supertype-Subtype Relationship

A subtype relationship is a relationship between a supertype entity and a subtype entity. You can use a subtype relationship to create a hierarchical grouping of entities that share common characteristics.

When you transition from one design layer to another, or when you change a model over time, the way that you represent subtype relationships can change. You can apply a transform to create an identifying relationship between a supertype entity and its subtype entities.

The main reasons why you apply a transform to create an identifying relationship between a supertype entity and its subtype entities include:

• You want to simplify a model.
• The subtype relationship is not appropriate for the current design layer.
• You want to improve query performance.

Supertype Subtype Identifying Wizard

To create an identifying relationship between a supertype entity and its subtype entities, you select the subtype relationship symbol , and click the Supertype-Subtype Identity icon in the Transforms toolbar. Use the Supertype Subtype Identifying Wizard to:

• Enter a name and definition for the transform.
• Specify whether future changes that you make to the new entity are applied, such as changing object properties or deleting objects, to the source entities. Specific rules are used when you change the new entity and you choose to apply the changes to the source entities.

Result of Creating an Identifying Relationship

When you click Supertype-Subtype Identify to create an identifying relationship between a supertype entity and its subtype entities, you:

• Convert the subtype relationships to identifying relationships.
• Add the transform to the Model Explorer under the Transforms folder.

Transforms in the Model Explorer

Each transform that you apply to model objects appears in the Model pane in the Model Explorer. By default, each transform is listed in alphabetical order under the Transforms folder.

You can right-click a transform in the Model Explorer and choose Properties to open the Modify Properties for Transform dialog. You use the Modify Properties dialog to change the transform name, add a definition, assign user-defined properties, and specify whether changes made to the target objects are applied to the source objects.

Automatically Resolving Subtype Relationships

To automatically resolve all subtype relationships on the logical side of a logical/physical model and create an identifying relationship between a supertype entity and its subtype entities on the physical side, select the Auto apply Supertype-Subtype Identity transform check box on the General tab of the Model Properties dialog. This check box is only available for logical/physical models.