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An extension point describes a point in a use case where
an extending use case may provide additional behavior.
Examples for a travel agent sales system might be the use
case for paying for a ticket, which has an extension point in
the specification of the payment. Extending use cases may then
extend at this point to pay by cash, credit card etc.
Within the UML metamodel, Extension
Point is a sub-class of
ModelElement. A use case may display an extension
point compartment (see Section 17.3, “Use Case” for
details), in which extension points are shown with the
following syntax.
17.4.1. Extension Point Details Tabs
The details tabs that are active for extension points
are as follows.
17.4.2. Extension Point Property Toolbar
Go upNavigate up to the use case which owns this
extension point.
New Extension PointThis creates a new Extension Point below the
selected extension point, navigating immediately to the
properties tab of the newly created extension
point.
New StereotypeThis creates a new Stereotype (see
Section 16.6, “Stereotype”) for the selected
extension point, navigating immediately to the
properties tab for that stereotype.
DeleteThis deletes the selected extension point from
the model.
17.4.3. Property Fields For Extension Point
NameText box. The name of the extension point.
![[Tip]](images/tip.png) | Tip |
|---|
It is quite common to leave extension points
unnamed in use case analysis, since they are always
listed (within use cases and extend relationships) by
their location. |
![[Note]](images/note.png) | Note |
|---|
ArgoUML does not enforce any naming convention
for extension points. |
LocationText box. A description of the location of this
extension point within the owning use case.
| Tip |
|---|
Extension points are always listed (within use
cases and extend relationships) by their location.
Typically this will be the number/name of the
paragraph in the specification. |
Base Use CaseText box. Shows the base use case within which
this extension point is defined. Button 1 Double Click
will navigate to the use case.
ExtendText box. Lists all use cases which extend the
base use case through this extension point.
Where an extending use case exists, button 1
double click will navigate to that relationship.
