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Lesson 1.3: Identify actors

In this lesson, you identify the actors of the system. The Account Operations use-case diagram identifies the key actors and the roles that they perform in the system. You must identify all the actors before you can create the diagram.

About this task

You should understand who the users of the system are before you begin to model it. In a use-case diagram, users of the system are depicted as actors. Each actor performs a specific role in the system, which is called a use-case. More than one actor can perform a single use-case. An actor can be a person, such as a customer, or a computer, such as a database system or server.

The Account Operations use-case diagram contains detailed information about the PiggyBank online banking system, the system's users, relationships between the system and the users, and the required behavior of the system. The previous lesson identified three use cases: Display Balance, Transfer Money, and Cash Check. The PiggyBank online banking system contains the following actors:

  • Customer
  • Teller
  • CityBank

To create the diagram and identify the actors:

Procedure

  1. In the Project Explorer view, in the PiggyBank project, double-click Account Operations Use Cases.
  2. In the Palette, double-click Actor and name the actor Customer.
  3. Click the Customer actor and drag it to the left of the Display Balance use-case.
  4. In the Palette, double-click Actor and name the actor Teller.
  5. Click the Teller actor and drag it to the left of the Cash Check use-case.
  6. In the Palette, double-click Actor and name the actor CityBank.
  7. Click the CityBank actor and drag it to the right of the Cash Check use-case.

Results

You have now organized the use-case diagram according to the Rational® UML model structure guidelines. The prime actor appears in the top-left corner of the diagram and the most important use-case appears above all other use-cases. The secondary actor, CityBank, appears to the right of the use-cases. Your diagram should look similar to the following figure:The actors and use cases of the PiggyBank use-case diagram.

(Optional) Document the actors

About this task

The use-case model template contains an overview package called <<perspective>> Overviews that provides additional documentation about the model. Although this step is optional and does not impact the model, you should organize and document the actors and use cases in the PiggyBank online banking system.

Procedure

  1. In the Project Explorer view, expand <<perspective>> Overviews and double-click Actors Overview. This diagram will contain a list of the main use-cases in the project.
  2. In the Project Explorer view, expand the Account Operations folder and drag the Customer, Teller, and CityBank actors into the diagram editor.
  3. Arrange the use-cases vertically in the center of the diagram.

Results

You have now increased the readability of this use-case model by documenting the project's significant actors. You can add a title to the diagram by using the text tool. Also note that the use-case template contains a Versatile Actors package which you can use to document all the actors that participate in several functional areas. Because this model contains no versatile actors, you can delete this package by right-clicking it; then clicking Delete from Model.
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