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 16.1, “Possible artifacts 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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![[Warning]](images/warning.png) | Warning |
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The current release of ArgoUML does not preserve information about whether the extension point compartment is showing on save. On reload, no compartments will be visible. | |
The details tabs that are active for use cases are as follows.
ToDoItemStandard tab.
PropertiesSee Section 16.3.2, “Use Case Property Toolbar” and Section 16.3.3, “Property Fields For Use Case” below.
DocumentationStandard tab. See Section 12.5, “Documentation Tab”.
StyleStandard tab. 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.Caution The
Shadowfield has no effect on use cases.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.
ConstraintsStandard tab. ArgoUML only supports constraints on Classes and Features (Attributes, Operations, Receptions, and Methods), so this tab is grayed out.
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.
Go upNavigate up through the package structure of the model.
Add use caseThis creates a new use case within the model, (but not within the diagram), navigating immediately to the properties tab for that use case.
Tip This method of creating new use cases can be confusing. Much better to create them within diagrams where you want them.
Add 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.
DeleteThis deletes the selected use case from the model.
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.Note ArgoUML does not enforce any naming convention for use cases
StereotypeDrop down selector. Use case is provided by default with the UML standard stereotypes (
metaclass,powertype,process,thread,utility) for classifiers. Stereotyping can be useful when creating use cases in the problem domain (requirements capture) and solution domain (analysis), but none of the predefined stereotypes are well suited to this.Navigate Stereotype
icon. If a
stereotype has been selected, this will navigate to the
stereotype property panel (see Section 15.4, “Stereotype”).NamespaceText box. Records the namespace for the use case. This is the package hierarchy.
ModifiersCheck box, with entries
leafandroot.leafindicates that this use case can have no further children, whilerootindicates it is a top level use case with no parent.
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 one entry.
New. Add a new extension point and navigate to it, making this use case the owning use case of the extension point.
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.
Association EndsText box. Lists any association ends (see Section 17.11, “Association”) of associations connected to this use case.
Button 1 double click navigates to the selected entry.