Which UML diagram should be used to display the order of interaction when processing an order?

To display the order interaction sequence during the checkout process, it is best to use a Sequence Diagram from UML.

It shows how objects interact with each other over time, displaying the sequence of messages and calls between the participants in the process. This helps to understand the order in which actions occur and how data is transferred between system components.

Examples of the main elements of a sequence diagram:

• Participants (actors and objects)
• Messages (method calls, responses)
• A timeline from top to bottom

This approach visually demonstrates the order of the checkout process step by step.