About Use Case

A use case is a coherent unit of functionality provided by a system or class as manifested by sequences of messages exchanged among the system and one or more outside interactors (called actors), together with actions performed by the system. A use case diagram shows the relationship among actors and use cases within a system. You can find examples of use case diagrams in the samples folders in your Together installation.

When you create a Use Case node on the diagram, you can either use its Note property or the Doc tab in the Inspector to write and store the actions for that Use Case.  If you use the Note property, it is displayed as a visual node on the Use Case diagram and when you invoke Generate Documentation feature. The notes are automatically included in the documentation produced.

Main Use Case elements

Actor

An actor is a role of an object (or objects) outside of a system that interacts directly with it as part of a coherent work unit (a use case). An Actor element characterizes the role played by an outside object; one physical object may play several roles and therefore be modeled by several actors.

Actor properties

You can edit name in place on the Actor icon or in the Inspector. Name displays in the Diagram pane as a label for Actor unless you specify a value for alias, in which case the Actor icon is labeled with that value. The stereotype drop-down list presents the UML stereotypes for  Actor, but you can enter any value. (The list of stereotypes can be customized in .\lib\config.properties. Search for the line: inspector.all.tag.all.Actor.stereotype.values).

 Use Case Links

There are several standard relationships among use cases or between actors and use cases. These are:
 

	Communicates The participation of an actor in a use case. This is the only relationship between actors and use cases. It is not applicable between Actors.
	Extends An extends relationships from use case A to use case B indicates that an instance of use case B may include (subject to specific conditions specified in the extension) the behavior specified by A. Behavior specified by several extenders of a single target use case may occur within a single use case instance.
	Uses A uses relationship from use case A to use case B indicates that an instance of the use case A will also include the behavior as specified by B.

 

Chapter contents

About Use Case
Main Use Case Elements
Actor
Actor properties
Use Case Links