Chapter 4 Building Conceptual Data Models

Defining cardinality for an association link

Cardinality indicates the number of occurrences (one or many) that one entity has relative to another. You define the cardinality for each association link between the association and the entity.

The cardinality of an association link can have the following values:

Cardinality Description
0,1 There can be zero or one occurrence of the association in relation to one instance of the entity. The association is not mandatory
0,n There can be zero or many occurrences of the association in relation to one instance of the entity. The association is not mandatory
1,1 One occurrence of the entity can be related to only one occurrence of the association. The association is mandatory
1,n One occurrence of the entity can be related to one or many occurrences of the association. The association is mandatory

You can change the default format of cardinalities from the registry:

HKEY_CURRENT_USER\Software\Sybase\PowerDesigner 11\ModelOptions\Conceptual Options
CardinalityNotation=1 (0..1) or 2 (0,1)

Steps To define cardinality for an association link:

  1. Double-click the association link between an association and an entity to display the association link property sheet.
  2. Select a cardinality from the Cardinality list.
  3. Click OK.

    You can repeat the procedure for each association link.

 

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