A use case represents a complete meaningful “chunk” of activity by the system in relation to its external users (actors), human or machine. It represents the primary route through which requirements are captured for the system under construction
Within the UML metamodel, use case is a sub-class of
classifier.
The use case icon is an oval (see Figure 17.1, “ Typical model elements on a use case diagram. ”). It may be split in two, with the lower compartment showing extension points
![[Caution]](images/caution.png) | Caution |
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By default ArgoUML does not show the extension point
compartment. It may be revealed by the context sensitive
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The details tabs that are active for use cases are as follows.
ToDoItemStandard tab.
PropertiesSee Section 17.3.2, “ Use Case Property Toolbar ” and Section 17.3.3, “ Property Fields For Use Case ” below.
DocumentationStandard tab. See Section 13.4, “ Documentation Tab ”.
PresentationStandard tab. The Fill color is used for the use case oval.
The
Display: Extension Pointscheck box is used to control whether an extension point compartment is displayed.SourceStandard tab. It would not be usual to provide any code for a use case, since it is primarily a vehicle for capturing requirements about the system under construction, not creating the solution.
StereotypeStandard tab.
Tagged ValuesStandard tab. In the UML metamodel,
UseCasehas the following standard tagged values defined.persistence(from the superclass,Classifier). Valuestransitory, indicating state is destroyed when an instance is destroyed orpersistent, marking state is preserved when an instance is destroyed.![[Tip]](images/tip.png)
Tip In general the instantiation of use cases is not a major aspect of any design method (they are mostly concerned with requirements capture. For most OOA&D methodologies, this tag can safely be ignored.
semantics(from the superclass,Classifier). The value is a specification of the semantics of the use case.derived(from the superclass,ModelElement). Valuestrue, meaning the use case is redundant -it can be formally derived from other elements, orfalsemeaning it cannot.![[Note]](images/note.png)
Note Derived use cases still have their value in analysis to introduce useful names or concepts.
ChecklistStandard tab for a Classifier.
Go upNavigate up through the package structure of the model.
New use caseThis creates a new use case within the model, (but not within the diagram), and shows immediately the properties tab for that use case.
Tip This method of creating a new use case can be confusing. It is much better to create a new use case on the diagram of your choice.
New extension pointThis creates a new use extension point within the namespace of the current use case, with the current use case as its associated use case, navigating immediately to the properties tab for that extension point.
New AttributeThis creates a new attribute within the current use case, navigating immediately to the properties tab for that attribute.
New OperationThis creates a new operation within the current use case, navigating immediately to the properties tab for that operation.
New ReceptionThis creates a new reception within the current use case, navigating immediately to the properties tab for that reception.
New StereotypeThis creates a new stereotype within the current use case, navigating immediately to the properties tab for that stereotype.
DeleteThis deletes the selected use case from the model.
![[Warning]](images/warning.png)
Warning This is a deletion from the model not just the diagram. To delete a use case from the diagram, but keep it within the model, use the main menu
Remove From Diagram(or press the Delete key).
NameText box. The name of the use case. Since a use case is a classifier, it would be conventional to Capitalize the first letter (and initial letters of any component words), e.g.
RemoteSensor. The name is shown inside the oval representation of the use case on the diagram.Note ArgoUML does not enforce any naming convention for use cases
NamespaceText box with navigation button. Records the namespace for the use case. This is the package hierarchy.
ModifiersCheck box, with entries
AbstractLeafandRoot.Abstractis used to declare that this actor cannot be instantiated, but must always be specialized. .Leafindicates that this use case can have no further children, whileRootindicates it is a top level use case with no parent.
Client DependenciesText area. Lists the “depending” ends of the relationship, i.e. the end that makes use of the other end.
Button 1 double click navigates to the dependency and opens its property tab.
Button 2 click shows a pop-up menu with one entry
Add...that opens a dialog box where you can add and remove depending modelelements.Supplier DependenciesText area. Lists the “supplying” ends of the relationship, i.e. the end supplying what is needed by the other end.
Button 1 double click navigates to the dependency and opens its property tab.
Button 2 click shows a pop-up menu with one entry
Add...that opens a dialog box where you can add and remove dependent modelelements.GeneralizationsText area. Lists use cases which are generalizations of this one. Will be set whenever a generalization is created on the from this Use Case. Button 1 Double Click on a generalization will navigate to that generalization.
SpecializationsText box. Lists any specialized use case (i.e. for which this use case is a generalization.
Button 1 double click navigates to the generalization and opens its property tab.
ExtendsText box. Lists any class that is extended by this use case.
Where an extends relationship has been created, button 1 double click will navigate to that relationship.
IncludesText box. Lists any use case that this use case includes.
Where an include relationship has been created, button 1 Double Click will navigate to that relationship.
AttributesText area. Lists all the attributes (see Section 18.7, “ Attribute ”) defined for this use case. Button 1 double click navigates to the selected attribute. Button 2 gives a pop up menu with two entries, which allow reordering the attributes.
Move Up. Only available where there are two or more attributes listed, and the attribute selected is not at the top. It moves the attribute up one position.Move Down. Only available where there are two or more attributes listed, and the attribute selected is not at the bottom. It moves the attribute down one position.
Association EndsText box. Lists any association ends (see Section 18.12, “ Association ”) of associations connected to this use case.
Button 1 double click navigates to the selected entry.
OperationsText area. Lists all the operations (see Section 18.8, “ Operation ”) defined on this use case. Button 1 click navigates to the selected operation. Button 2 gives a pop up menu with two entries, which allow reordering the operations.
Move Up. Only available where there are two or more operations listed, and the operation selected is not at the top. It moves the operation up one position.Move Down. Only available where there are two or more operations listed, and the operation selected is not at the bottom. It moves the operation down one position.
Extension PointsText box. If this use case is, or can be extended, this field lists the extension points for the use case.
Note Extension points are listed by their location point rather than their name.
Where an extension point has been created (see below), button 1 Double Click will navigate to that relationship. Button 2 gives a pop up menu with the following entries.
New. Add a new extension point and navigate to it, making this use case the owning use case of the extension point.Move Up. Only available where there are two or more extension points listed, and the extension point selected is not at the top. It moves the extension point up one position.Move Down. Only available where there are two or more extension points listed, and the extension point selected is not at the bottom. It moves the extension point down one position.