Simplifying Use Cases - Extend - Extension Points

8 important questions on Simplifying Use Cases - Extend - Extension Points

There exists additional notation that helps in identifying when and where to insert the extension.

What is this additional notation?

We can attach a constraint to the «extend» arrow, indicating the condition that must be true for the extension to be applied.

We use the standard constraint notation, a note symbol, with the label “condition.”

What are extension points?

We can also place inside the extended Use Case a list of locations, called extension points.

These are locations where the extension can be inserted if the condition is true.

UML doesn’t have a standard way of identifying these list of locations.

But what is commonly of naming  these list of locations?

Commonly they are the name of a state in a state machine for the Base Use Case.

What does UML says about the use of extension points?

Both the extension points and condition are optional.

You can use neither, either, or both. 

What does a condition mean in a use case diagram?

The condition can refer to an extension point to indicate where the condition will be tested.

What is an alternative format for the Use Case and extension points?

Using a Classifier Rectangle.

When is it useful to use the Classifier Rectangle?

It is sometimes more useful when there are many extension points or when inheritance is involved.

What does the oval in the upper right mean?

The Use Case oval in the upper right gives a visual indication that the classifier represents a Use Case.

The compartment name is “extension points.”

The question on the page originate from the summary of the following study material:

  • A unique study and practice tool
  • Never study anything twice again
  • Get the grades you hope for
  • 100% sure, 100% understanding
Remember faster, study better. Scientifically proven.
Trustpilot Logo
  • Higher grades + faster learning
  • Never study anything twice
  • 100% sure, 100% understanding
Discover Study Smart