Exercise 2.5: Creating the Display Balance participants diagram

In this exercise, you create the Display Balance participants diagram. The Display Balance participants diagram models the static structure of the Display Balance use case.

The Display Balance participants diagram shows the classes that participate in the Display Balance use case. You model the participants, along with their attributes and relationships, to describe the domain of the system. In addition to entities, this diagram describes the boundary classes that interact with the main entity classes to complete the functional task. A menu and a computer interface are examples of boundary classes.

Modeling is an iterative process. You can add, remove, or modify particpants at any time as you better understand the details of the system that you are modeling. In this tutorial, you create the basic outline of the Display Balance participants diagram. You add to this diagram as you model the dynamic structure of the use case.

Creating the diagram and modeling the Account participant

You create the Display Balance participants diagram in the Account Operations package.

To create the diagram and model the Account class:
  1. In the Model Explorer view, expand Analysis Model, expand Account Operations, expand «use case realization» Display Balance, and double-click «use case realization» Display Balance Participants.
  2. In the Model Explorer view, expand Account Operations Analysis Elements, click the Account class, and drag it into the diagram.

You have created the Account participant by dragging the Account model element that was created in the domain diagram exercise. The Account participant is the only element in the Display Balance Participant diagram.

Creating the DisplayBalanceForm participant

The DisplayBalanceForm participant represents a boundary class that exists between the main PiggyBank main menu and the Account class.

To create the DisplayBalanceForm participant:
  1. In the Palette, double-click Class and name the class DisplayBalanceForm.
  2. In the diagram editor, click the DisplayBalanceForm class and, in the Properties view, on the Stereotypes page, click Add Stereotypes.
  3. In the Apply Stereotypes window, select Boundary, and click OK.
  4. In the Palette, click the Usage element.
  5. In the diagram editor, place the cursor over the DisplayBalanceForm class and drag it to the Account class.

You have just modeled the DisplayBalanceForm boundary particpant. The DisplayBalanceForm class has a single relationship to the Account class. Your diagram should look similar to the following figure:

The DisplayBalance and Account classes share one usage relationship.

Modeling the static structure of the Display Balance use case provides you with a better understanding of the main classes that participate in the use case. After you understand the main class structure, you can model the workflow of the use case by creating the Display Balance sequence diagram. When you create the Display Balance sequence diagram, you identify the operations of each entity in the use case. The sequence diagram can help you to better understand the data flow in the use case.

To continue, proceed to Exercise 2.6: Creating the Display Balance sequence diagram.

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