Tutorial

Quick definition of a UML use case diagram

A use case diagram can be used to describe the usage requirements for a system from an external point of view.

Goal of this tutorial

The goal of this tutorial is to show how to create a UML use case diagram in Modelio. For the purposes of this tutorial, we will use the following example diagram found on the web:

(This diagram comes from Wikipedia)

Step-by-step tutorial

First of all, create or open a Modelio project.

This selection enables us to set a context for the diagram that we are creating so all the created model elements in the diagram will belong to this selected model element.

Step 2. Create a UML use case diagram.

We can create a use case diagram in two ways:

• Right-click on the selected element and select "Create a diagram...".
• Click on the "Create a UML/BPMN diagram..." button in the application toolbar.

Step 3. Select "Use Case diagram" in the left-hand list.

We can see that the context field is already completed. It corresponds to the element we selected. You can add a description indicating the goal of this diagram. This can be useful for other users if you want to share your project or even for you yourself if you want to generate documentation or simply to remember why you have created this diagram.

Step 4. Create the use cases, actors, communication links and extension relationships.

Here are some tips for the creation and the manipulation of these objects:

• Create several objects quickly (not available for links):
  1. Select an element.
  2. Press the CTRL key.
  3. Drag&drop the element.

• In this example, we suggest that you mask visibilty on communication links for practical reasons. Go to the "Configuration/Diagram styles..." menu, which opens the Diagram style editor. In the left list, select "use case" (which is under default) and then select "Association" in the right-hand table and click on the little arrow on the left of Association to see the graphic properties of Association. Uncheck the "Show visibility" property then save. By default, this option is activated and a visibility container is present (even if it is not directly visible). The visibility container appears sometimes when you try to click on the communication link so it can be a little disturbing.
  
• In the Diagram style editor, check "Show label" to show the label of the communication links.
• You can hide the line visible in the use cases (the line is used as separator for inner elements). Select a use case then change the display mode of inner elements to "Hidden".
  
• Apply the graphic properties of one object to other objects.
  1. Select an object.
  2. Click on the "Clone graphic options" button.
  3. Press on the "Alt" key and left-click on the object to which you want to apply the properties (repeat the step 3 as many times as needed).
  

Finally, it is just a question of graphically moving the objects to the right positions and choosing the right size for them. So, just play!