C4 model Note

Abstractions

Container

• Server-side web application

• Client-side web application

• Client-side desktop application

• Mobile app

• Server-side console application

• Microservice

• Serverless function

• Database

• Blob or content store

• File system

• Shell script

• etc

Core diagrams

Level 1: System Context diagram

Level 2: Container diagram

Level 3: Component diagram

Level 4: Code

Supplementary diagrams

• System Landscape diagram

• Dynamic diagram

• Deployment diagram

Notation

• Person

• Software System

• Container

• Component

• Relationship

Diagram key/legend

Notation, notation, notation

A software architecture diagram review checklist

Examples

• Big Bank plc (System Landscape, System Context, Container, Component, Dynamic and Deployment)

• Financial Risk System (System Context)

• Spring PetClinic (System Context, Container, Component, Dynamic and Deployment)

• Message bus and microservices (Container and Dynamic)

• Widgets Limited (System Landscape, System Context and Dynamic)

• Contoso University (System Context, Container, Component and Dynamic)

Frequently asked questions

What’s the inspiration behind the C4 model?

1. make it easier for software developers to describe and understand how a software system works

2. minimise the gap between the software architecture model/description and the source code

Tooling

• Structurizr

• Structurizr for Java/.NET + PlantUML

• c4-draw.io

  • Extras → Plugins → Add: https://tobiashochguertel.github.io/c4-draw.io/c4.js

References

• The C4 model for visualising software architecture