How to Create UML State Machine Diagram with Trigger Events

Step 1: Setting Up Your Class Diagram

Begin by creating or opening a class diagram in Software Ideas Modeler. For this tutorial, we're using an Order class with five operations: PlaceOrder, StartProcessing, ConfirmShipping, ConfirmDelivery, and Cancel.

Step 2: Creating a State Machine Diagram

• Add a Nested Diagram: Right-click on the Order class to open the context menu. Navigate to the "Diagrams" submenu and select "Add Nested Diagram". This action opens the New Diagram dialog.
• Select Diagram Type: In the dialog, choose "State Machine Diagram" from the list of diagram types. Name it "Order States" and click the OK button. This adds a new State Machine Diagram, nested within the Order class element.

Step 3: Adding States

• Add an Initial State: From the State Machine Diagram toolbox, select the Initial State symbol and drag it onto the canvas. Clear its default name for simplicity.
• Create Named States: Drag the State element from the toolbox onto the canvas and name it "New". Repeat this process to add other states: Processing, Shipped, Delivered, and Cancelled.

Step 4: Defining Transitions

• Select the Transition Tool: Click on the Transition button in the toolbox to activate the tool. Click again to lock it, allowing you to add multiple transitions without reselecting the tool.
• Draw Transitions: Drag from the New state to the Processing state, from Processing to Shipped, and from Shipped to Delivered. These transitions represent the order's progression through its lifecycle.

Step 5: Adding Cancel Transitions

• Select Multiple States: To demonstrate a method for adding transitions to the Cancelled state from any state, select the New, Processing, and Shipped states by pressing and holding CTRL.
• Create Cancel Transitions: Drag a Transition from each selected state to the Cancelled state. This action illustrates that an order can be cancelled from almost any state.

Step 6: Setting Trigger Events for Transitions

• Open Transition Properties: Double-click on a transition to open its Properties dialog. Navigate to the Triggers tab and click "Add New".
• Define a New Event: Choose "New event" and name it according to the operation it represents, such as PlaceOrder. In the Event Definition section, select the "Call" radio button and choose the corresponding operation from the dropdown.
• Use the Element Picker: If you have many operations, click on the ellipsis button to open the Element Picker dialog. This tool allows you to search for and select an operation easily.

Step 7: Reusing Events

For transitions that trigger the same event, use the "Add Existing" button in the transition's Properties dialog to assign a previously defined event, like Cancel, to other transitions.

Step 8: Finalizing the Diagram

For states that represent an end to the process, like Cancelled and Delivered, use the right mouse button to drag from the state and choose "Add Transition to Final State". This action adds a final state to indicate the end of the process.

Step 9: Review and Save

• Review Your Diagram: Ensure all states, transitions, and trigger events are correctly represented in your diagram.
• Save Your Work: Once satisfied with your State Machine Diagram, save your project in Software Ideas Modeler.