Extend Relationship
Last updated
Last updated
An Extend Relationship in a Use Case Diagram represents a situation where one Use Case (the extending Use Case) may be used to augment the behavior of another Use Case (the base Use Case) under certain conditions.
With Extend Relationships in Modeldraw's Use Case Diagram, you can:
Show optional or conditional behavior in your Use Cases
Represent alternative flows or exceptional scenarios
Add flexibility to your Use Case model
Separate core functionality from optional or specialized behavior
Illustrate how a system can be extended without modifying the base Use Cases
Manage complexity by breaking down Use Cases into more manageable pieces
An Extend Relationship in Modeldraw's Use Case Diagram tool is typically represented by a dashed arrow with an open arrowhead, pointing from the extending Use Case to the base Use Case, labeled with the stereotype «extend». Key points to understand about Extend Relationships include:
The extending Use Case is only executed under specific conditions.
The base Use Case is complete on its own and may or may not include the extending Use Case.
The arrow points from the extending Use Case to the base Use Case.
The base Use Case may define specific points where the behavior can be extended.
It helps in separating core functionality from optional or specialized behavior.
Extend Relationships allow for system extensibility without modifying existing Use Cases.
To create an Extend Relationship in Modeldraw's Use Case Diagram:
Select the Extend Relationship tool from the toolbox.
Click on the extending Use Case (the one that provides the optional behavior).
Move your mouse to the base Use Case (the one that may be extended).
Click on the base Use Case. An Extend Relationship arrow will appear, pointing from the extending Use Case to the base Use Case.
The relationship will be automatically labeled with the «extend» stereotype.
