Chapter 4 Building Conceptual Data Models

Defining a dominant relationship

In a one-to-one relationship, you can define one direction of the relationship as dominant. If you define a dominant direction, the one-to-one relationship generates one reference in the PDM. The dominant entity becomes the parent table. If you do not define a dominant direction, the one-to-one relationship generates two references.

To define a dominant relationship:

1. Double-click a relationship symbol in the diagram to display the relationship property sheet.
   
   It displays the definition of the selected relationship.
2. Click the Cardinalities tab to display the corresponding page.
3. Select the One to One check box.
4. Select the direction for the dominance from the Dominant Role list.
5. Click OK.

Example

For example, in the property sheet below, the Author to Picture direction is dominant in the relationship.

The relationship pictured here shows the one-to-one relationship.

In a PDM, this relationship generates the following reference: Author is the parent table, and its primary key migrates to the Picture table as foreign key.

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