Sequence Diagram

A sequence diagram is a type of UML (Unified Modeling Language) diagram that shows how objects interact in a particular sequence. It is commonly used to visualize the flow of messages, operations, or events between objects.

Components of a Sequence Diagram

The diagram consists of the following components:

• Actors: Represent users or other systems interacting with the system.
• Objects: Represent entities or classes involved in the interaction.
• Lifelines: Represent the lifetime of an object during the interaction.
• Messages: Represent the communication between objects (solid arrows for synchronous calls and dashed arrows for responses).
• Activation Bars: Indicate the period an object is performing a task.

 

Example

 

sequenceDiagram
 participant User
 participant LoginPage
 participant AuthService
 participant Database

 User->>LoginPage: Enter Username and Password
 LoginPage->>AuthService: Send Credentials
 AuthService->>Database: Validate Credentials
 Database-->>AuthService: Validation Result
 AuthService-->>LoginPage: Login Success/Failure
 LoginPage-->>User: Display Result

Scenario: A user logs into a system with a username and password.

Actors and Objects:
Actor: User
Objects: Login Page, Authentication Service, Database

Steps
User enters credentials on the Login Page.
Login Page sends the credentials to the Authentication Service.
Authentication Service validates the credentials by querying the Database.
Database responds with the validation result.
Authentication Service sends the success or failure response back to the Login Page.
Login Page displays the result to the User.