Teams also rely on sequence diagrams to analyze current workflows. However, one of the primary use cases for sequence diagrams is in requirements documentation for future system implementations, where they are used to model how a new system will function and behave, ensuring clarity during the design and development phases.
How to use the UML Sequence Diagram template
FigJam is an ideal online tool for creating sequence diagrams from scratch and easily sharing them with your team. FigJam also offers a customizable UML sequence diagram template. To get started, simply select the template and follow these steps:
- Identify Your Lifelines
Lifelines represent roles or object instances interacting in the sequence. There can be two or more lifelines, each placed in a box at the top of the diagram with a vertical dashed line extending below.
- Create Messages
Messages depict interactions between lifelines and are represented by horizontal arrows. There are seven different types of messages that can be used in a sequence diagram, depending on the interaction.
- Define Your Actor
An actor is an external entity interacting with the sequence but not part of it. For example, in an online shopping sequence, the "actor" is the customer, while the shopping system's steps (e.g., "Add to cart," "Total," "Confirm order") form the sequence.
- Add Activation Bars
Activation bars are thin rectangles placed under a lifeline to indicate the duration of a task. You can add multiple activation bars on the same lifeline to show overlapping actions.
- Include Other Key Features
For more complex diagrams, you can add Alternatives, Options, and Loops to represent variations in the sequence, such as different scenarios or repeating actions.
Examples of a UML sequence diagram
Let’s use the example of a fast-food restaurant's ordering system to understand how a sequence diagram works.
In this scenario, the following interactions occur when a customer places an order:
- The customer goes to the cash counter and places their order.
- The cashier confirms the order and passes the order details to the kitchen.
- The kitchen staff prepare the food and send it back to the counter.
- The cashier hands the order to the customer.
In the sequence diagram for this scenario, the three lifelines would be the Customer, the Cashier, and the Kitchen. Each of these lifelines represents an active role in the system, and they communicate by delivering messages back and forth.
The key actions that take place during this sequence are the messages, such as:
- "Place an order" (Customer to Cashier)
- "Order confirmation" (Cashier to Customer)
- "Order details for preparation" (Cashier to Kitchen)
- "Order delivery" (Kitchen to Cashier, then Cashier to Customer)
This sequence diagram visually maps how these objects interact in sequential order, showing the flow of operations from placing the order to receiving the food.
Benefits of using the UML sequence diagram template
Let’s explore four key benefits of using a sequence diagram template:
- Identify Interface and Logical Issues Early
By creating a sequence diagram, teams must outline all the system's details, helping them spot potential issues or inconsistencies before the implementation phase.
- Enhance Team Collaboration
Sequence diagrams are ideal for clearly illustrating how a system functions during meetings or collaborative projects, making them an effective tool for teamwork and communication.
- Gain a High-Level Overview
Sequence diagrams allow analysts to view a system at various levels of detail. Whether it’s a shopping kiosk or an app, you can start with a broad overview and then zoom in on specific components as needed.
- Easily Update and Modify
Teams can easily update the elements of a sequence diagram to reflect new events or changes, without having to redo the entire diagram, making it a flexible and adaptable tool.
