A Simple Way to Visualizing Software Architecture

Effectively communicating the structure and design of a system is crucial. Whether you’re explaining your architecture to a new team member or documenting it for future reference, clarity is key. But how do you document your architecture? And at what level?

This is where the C4 Model comes into play. Developed by Simon Brown, the C4 Model offers a clear and structured way to visualize software architecture, making it easier for everyone involved to understand and work with the system.

What is the C4 Model?

The C4 Model is a framework for visualizing software architecture at different levels of detail. The name “C4” stands for Context, Containers, Components, and Code. Each level provides a different perspective on the system, allowing you to zoom in and out as needed:

1. Context Diagram: Shows how your system fits into and interacts with its environment.
2. Container Diagram: Breaks down the system into high-level containers such as web servers, databases, and microservices. And no - we are not talking about Docker containers.
3. Component Diagram: Details the components within each container and their interactions (Controllers, Services etc).
4. Code (or Class) Diagram: Offers a detailed view of the code, typically at the class / file level.

The Four Levels of the C4 Model

1. Context Diagram

At the highest level, the Context Diagram provides a big-picture view of the system and its interactions with external entities such as users, external systems, and services. This diagram answers the question: “What is the system and who does it interact with?”

2. Container Diagram

The Container Diagram zooms in to show the high-level building blocks of the system. Containers represent applications or services that execute code or store data. This diagram answers the question: “What are the major technical building blocks of the system?”. At this level you will find for instance email servers and web servers.

3. Component Diagram

The Component Diagram delves deeper into each container to show the components within them. Components are the logical parts of the system, such as controllers, services, APIs, and databases. This diagram answers the question: “What are the components within each container and how do they interact?”

4. Code (or Class) Diagram

At the most detailed level, the Code Diagram shows the internal structure of a component, typically at the class / files level. This diagram answers the question: “How is the component implemented?”

Benefits of the C4 Model

Clarity and Simplicity

The C4 Model’s structured approach helps in breaking down complex systems into manageable parts. Each diagram focuses on a specific level of detail, making it easier to understand and communicate the system’s architecture.

Flexibility

The C4 Model is not tied to any specific technology or methodology. Whether you’re working with microservices, monoliths, or serverless architectures, the C4 Model can be adapted to fit your needs.

Improved Communication

By providing a common language and set of diagrams, the C4 Model facilitates better communication among team members, stakeholders, and external partners. It helps ensure that everyone has a shared understanding of the system.

Documentation

The C4 Model makes it easier to create and maintain comprehensive documentation. Each diagram can be used as part of your architecture documentation, providing a clear and consistent way to describe the system.

Getting Started with the C4 Model

To start using the C4 Model, you don’t need any special tools. Simple drawing tools like Google Draw, MS Visio, Lucidchart, or even pen and paper can be used to create the diagrams.

Here are a few steps to get started:

1. Identify the scope: Determine the boundaries of the system you want to model.
2. Create the Context Diagram: Identify external entities and how they interact with your system.
3. Create the Container Diagram: Break down the system into high-level containers (NOT docker containers!)
4. Create the Component Diagram: Zoom into each container to identify and document the components (Controllers, Services).
5. Create the Code Diagram: If needed, provide a detailed view of the implementation. (Class or file level).

Conclusion

The C4 Model offers a simple yet powerful way to visualize and document software architecture. By breaking down the system into different levels of detail, it helps ensure that everyone involved has a clear understanding of how the system works. Whether you’re a seasoned architect or a developer new to the field, the C4 Model can be a valuable tool in your toolkit.

More:

• The amazing Simon Brown published the C4 Model under the creative commons license. Thanks!
• Schematic sketch of C4 Model displayed above is provided by https://c4model.com/img/c4-overview.png under the creative commons license.
• https://en.wikipedia.org/wiki/C4_model