Use case (dictionary item)

Model Parts, Diagrams, Dictionary Items, and Properties > Dictionary items > Use case (dictionary item)

For automation interface information about a Use Case, see Use case (automation interface).

A Use Case is a set of operations performed by the system being modeled whose purpose is to provide a piece of functionality of value to an Actor. A Use Case can represent a requirement of the system.

On Sequence Diagrams, instances of Use Cases are represented by Probes. A Probe represents the extend or include relationships between Use Cases in Sequence Diagrams and indicate the places where an extend or include Use Case is called.

A uses relationship is used to extract a common course of action. A used Use Case is not aware of what is using it.

An extend relationship models optional parts of use cases and provides additional functionality. An extend use case knows how to insert itself into a basic use case.

You can create a Use Case through the context menu of a Package: right-click the Package, and select New > UML > Use Case > Use Case. You can also create a Use Case through a Class Diagram, Use Case Diagram or Sequence Diagram.

When used on a Class Diagram or Use Case Diagram, a Use Case's notation is as follows:

For information about the View Options available for this symbol, see Use case view options — class diagram.

When used as a Probe on a Sequence Diagram, a Use Case's notation is as follows:

For information about the View Options available for this symbol, see Probe view options sequence diagram.

In the Modeler panes, a short-cut symbol

on the Use Case's icon indicates that the item is a stub.

If you select the UML\Use Cases folder in the Dictionary pane, the Contents pane displays the following information about each Use Case in the model: Name, Initial Event, Visibility, Package, Changed By and Changed On.

The following sections provide information about how a Use Case is used in the model. For more information about a property, item, model part or diagram, click it.

Properties

In addition to the standard properties, a Use Case has these properties:

• Alternate Courses

• Intent

• Post Conditions

• Pre Conditions

• Timing Note

• Visibility

An instance of a Use Case (Uses Probe or Extends Probe) on a Sequence Diagram has these properties:

• Actual Parameters (Name)

Owned by

Owns

Dependency — The Dependency is owned jointly by the Use Case and the other associated item. The access permissions you have to a Dependency are determined by the access permissions of the dependent item.

Generalization — The Generalization is owned jointly by the Use Cases it links. The access permissions you have to a Generalization are determined by the access permissions you have to the child Use Case.

A Use Case can own these diagram types:

Communication Diagram

General Flow Diagram

Sequence Diagram

State Machine

Defined in these parts of the model

Use Case Model

Used in:

Concurrency Model

Object Interaction Model

Shown on these diagrams

Class Diagram

Use Case Diagram

Instances of a Use Case (probe) can appear on these diagrams.

Sequence Diagram

Variant Diagram

For information about how the View Options affect the presentation of Use Cases, see Use case view options use case diagram.

Can be linked to these dictionary items

In addition to the owning Package or Model, a Use Case can be linked to the following items.

Activity — The linked Activity specifies the behavior that is invoked when you create an instance of the Use Case, that is, classifier behavior. The linked Activity must be owned by the Use Case, either directly or indirectly through inheritance. This link can be made through the Classifier Behaviors association on the Items tab of the Use Case's Property Pages.

Actor — The linked Actor performs or exchanges information with the Use Case. This link can be made by linking the items on a Use Case Diagram.

Atomic State — through the states relationship.

Concurrent State — - through the states relationship.

Entry State — through the states relationship.

Exit State — through the states relationship.

Final State — through the states relationship.

Fork State — through the states relationship.

History State — through the states relationship.

Increment — The Use Case is delivered by the linked Increment.

Initial State — through the states relationship.

Join State — through the states relationship.

Junction State — through the states relationship.

Sequential State — through the states relationship.

State Machine — The linked State Machine specifies the behavior that is invoked when you create an instance of the Use Case, that is, classifier behavior. The linked State Machine must be owned by the Use Case, either directly or indirectly through inheritance. This link can be made through the Classifier Behaviors association on the Items tab of the Use Case's Property Pages.

Stereotype

Submachine State — through the states relationship.

Like most other items in a Model, a Use Case can be linked to an Activity Partition, Comment, Frame Box, General Node, General Flow, General Flow Diagram Node, Constraint (applied), General Flow Diagram Flow or Swimlane.