Architectural Diagrams

These diagrams shift focus from code structure to the physical and logical organization of the system.

1. Component Diagrams

A Component is a modular part of a system that encapsulates its contents and whose manifestation is replaceable.

Symbols

• Component: A box with two small rectangles on the left or a stereotype <<component>>.
• Provided Interface: “Lollipop” symbol (circle on a line). The services the component offers.
• Required Interface: “Socket” symbol (half-circle). The services the component needs.

PlantUML Code:

package "Order System" {
  [Order Logic] --() IOrder
  [Payment Service] --() IPayment
}
[Web UI] ..> IOrder : use
[Order Logic] ..> IPayment : use

2. Deployment Diagrams

These diagrams show the physical hardware and software mapping.

Symbols

• Node: A 3D cube representing a physical or virtual machine (e.g., “Web Server”, “Database”).
• Artifact: A physical file (JAR, DLL, script) deployed on a node.
• Communication Path: A line representing the protocol (e.g., SSH, HTTP).

Example

PlantUML Code:

node "Application Server" {
  artifact "OrderService.jar"
}
node "Database Server" {
  database "PostgreSQL"
}
"Application Server" -- "Database Server" : JDBC / TCP:5432

Decisions: Component or Node?

• Component: Logical unit of code/functionality.
• Node: Physical or virtual environment where components “live”.