A role that some external entity adopts when interacting with the system DIRECTLY

Stakeholders who trigger the use case or cause the use case to be executed

Actor that interacts with the use case after it has been triggered

Include the behaviour of one use case into the flow of another use case

Do not create a hierarchical functional decomposition of the system by splitting a use case into several use cases

Provides a way to insert new behaviour into an existing use case

Generally not a complete use case, therefore it cannot be triggered by an actor

You can choose whether or not to execute the extension use case

Something that an actor wants the system to do

Start out with a verb, followed by a noun

Use present tense for verb, do not use continuous tense

What can the system do?

What does the actor want the system to do?

One actor can participate in all the associations with use cases that the more general actor can, plus some additional use cases

One use case provides all the functionality of the more general use case, and some additional functionality

A simple paragraph to describe what the use case does

Sub Topic

Used to help elicit requirements

Show how the user interface will look like for the client

Used to test out the system architectures for non-functional requirements

Who uses the system?

Who maintains the system?

Who owns the system?

What other system is the system using?

Helps model the analysis of usage requirements in the form of a system use-case model

Provide an overview of all or part of the usage requirements for a system

Helps communicate the scope of a project