Component Diagram

It is a structural diagram that shows how components are connected and how they interact to form larger software systems. It visualizes the organization and dependencies among a set of components.

What is a Component?

A component represents a modular part of a system that encapsulates its contents and defines its behavior in terms of provided and required interfaces. In simpler terms, components are self-contained units that can be replaced independently.

Components

1. Component:

• A self-contained module with well-defined functionality, like a class, module, or microservice.
• Represented as a rectangle with the stereotype «component».

  +------------------------+
  |      «component»       |
  |    Book Management     |
  +------------------------+

2. Interface:

• Defines how components communicate—what services they provide and require.
• Types:
  • Provided Interface (lollipop-○): what a component offers.
  • Required Interface (socket-◐): what a component needs.

3. Relationships:

• Dependency (dashed arrow): One component depends on another.
• Association (solid line): A structural link.
• Assembly Connector: Connects required to provided interfaces.

4. Ports:

• Interaction point on the boundary of a component.
• Represented as small square on the component’s edge.

5. Artifacts:

• A physical file or piece of code/data
• Real-world outputs like executable files or data.
• Shown as rectangles with «artifact».

6. Nodes:

• Physical/virtual environments where components run.
• Shown as 3D boxes.

Example:

                    +--------------------------+
                    |   «component»            |
                    |   UserInterface          |
                    |                          |
                    |   ◐ searchBooks()        |
                    |   ◐ borrowBook()         |
                    |   ◐ returnBook()         |
                    +----------◼--------------+
                               |
                               ▼
                    +--------------------------+
                    |   «component»            |
                    |   BookService            |
                    |   ○ searchBooks()        |
                    |   ◐ getBookDetails()     |
                    |   ◐ updateAvailability() |
                    +----------◼--------------+
                               |
                               ▼
                    +--------------------------+
                    |   «component»            |
                    |   LoanService            |
                    |   ○ borrowBook()         |
                    |   ○ returnBook()         |
                    |   ◐ calculateFines()     |
                    +----------◼--------------+
                               |
                               ▼
                    +--------------------------+
                    |   «component»            |
                    |   NotificationService    |
                    |   ○ sendDueAlert()       |
                    |   ○ sendOverdueNotice()  |
                    +--------------------------+

           (All components read/write to:)

                    +--------------------------+
                    |   «artifact»             |
                    |   LibraryDB.sql          |
                    +--------------------------+