How to Create a UML Communication Diagram: A Step-by-Step Guide

Help|Tutorials|UML|Diagramming|Video Tutorials| 5 September 2024 | Dusan Rodina - softwareideas.net
This article provides a step-by-step tutorial on creating a UML Communication Diagram using Software Ideas Modeler. It guides users through setting up a new diagram, adding actors and objects, and illustrating message-based communication between system components in an e-commerce checkout scenario.

Creating a UML Communication Diagram is an essential skill for modeling interactions between objects in a system, especially when you need to represent how components communicate during a process. In this tutorial, we’ll walk through the steps for building such a diagram using Software Ideas Modeler. For this example, we will design a diagram that illustrates the checkout process for an e-commerce system.

Step 1: Creating a New Diagram

  • Go to the Project Tab located in the ribbon at the top of the window.
  • Click on Add New Diagram.
  • A dialog box titled New Diagram will appear. Here, you need to:
    • Select UML diagrams from the category options (the list on the left).
    • Choose Communication Diagram from the available types.
    • In the Name field, type "E-commerce Checkout" as the name of the diagram.
  • Click OK to confirm.

Once you click the OK button, the system will add a new communication diagram to your project, and you will be presented with a blank canvas where you can start building the diagram.

Step 2: Adding Actors and Objects

To begin representing the participants in the process, we'll first add an Actor and a few Objects.

  • Add an Actor:
    • Find the Actor button in the toolbox on the left side of the screen.
    • Drag the Actor onto the diagram canvas.
    • Name the actor "Customer" by clicking on it and typing the label.
  • Add Objects:
    • Next, we'll represent the key objects in our system. To do this:
      • Drag the Object button from the toolbox to the canvas.
      • Name this object Shopping Cart. Since this is a generic object type and not a specific instance, enter the colon before the name such as ": Shopping Cart".
    • Repeat this process for two more objects:
      • Payment Gateway entered as ": Payment Gateway"
      • Inventory System entered as ": Inventory System"

Step 3: Connecting Objects with Messages

The core of the communication diagram is showing how these entities interact through messages.

  • Select the Message Tool:
    • Find the Message tool in the toolbox. To make it easier, hold the tool’s button for a moment to lock it, allowing you to draw multiple connections without reselecting it after each use.
  • Draw Message Connections:
    • Connect Customer to Shopping Cart by clicking and dragging between the two.
    • Connect Shopping Cart to Payment Gateway.
    • Connect Inventory System to Shopping Cart.

Step 4: Adding Sequence Expressions (Messages and Process Steps)

Now that the objects are connected, we can describe the specific interactions between them.

  • Add Steps for Customer to Shopping Cart:
    • Click on the message connector between Customer and Shopping Cart.
    • In the context bar, click on the Add Sequence Expression button and name this step "1. Add item to cart".
    • Add another sequence expression and name it "2. Place order".
  • Add Steps for Shopping Cart to Payment Gateway:
    • Select the connector between Shopping Cart and Payment Gateway.
    • Click on Add Sequence Expression and name the step "2.1 checkout" to indicate it's a substep within the second process.
    • Add a reverse step from Payment Gateway back to Shopping Cart using the Add Reverse Sequence Expression button in the context bar. Name this step "2.2 Process payment (paymentDetails)", which shows the payment details being sent back to the cart.
    • Add another reverse step, "2.3 Payment confirmation".
  • Add Steps for Shopping Cart to Inventory System:
    • Select the message connector between Shopping Cart and Inventory System.
    • Add a reverse sequence expression and name it "2.4 Update inventory (orderDetails)".
    • Add a forward sequence expression back to Shopping Cart, naming it "2.5 Inventory update confirmation".
  • Add Final Steps from Shopping Cart to Customer:
    • Finally, add an interaction from Shopping Cart back to Customer using the Add Reverse Sequence Expression button.
    • Name this step "2.6 Order confirmation", representing the final stage of the process.

Step 5: Review and Finalize the Diagram

Once you have added all the messages and sequence steps, take a moment to review the diagram and ensure the flow of communication is clear and logical.

  • Customer sends a message to Shopping Cart to add an item and place an order.
  • Shopping Cart communicates with the Payment Gateway to process the payment.
  • After the payment is processed, the Inventory System is updated with the order details.
  • Finally, the Customer receives an order confirmation.

Step 6: Save and Export Your Diagram

Now that your communication diagram is complete, don’t forget to save your project. You can also export the diagram in various formats (e.g., PNG, PDF, etc.) using the export options in the Process group in the Diagram ribbon tab.

New Comment

Comment