It is a huge challenge for teams in today's software development to design complex systems efficiently and to document their architectures clearly and sustainably. Well-structured and comprehensible documentation is often underestimated. This can lead to communication problems, maintenance issues or unexpected costs later on. This is where arc42 comes into play. This proven template for architecture documentation offers a systematic and practice-oriented solution for mastering these challenges and ensuring the long-term success of your software projects.

What is arc42?

arc42 is a comprehensive and field-tested template that has been specially developed for the documentation of software architectures. It offers a structured and modular approach to documenting all relevant aspects of a software architecture efficiently and comprehensibly. The template is flexibly customizable and suitable for projects of any size and complexity.

arc42 was developed by experienced software architects and has been used successfully in numerous projects worldwide. It covers all important areas, from basic decisions to system contexts and detailed architecture views. Thanks to its clear structure, arc42 enables transparent communication between all parties involved and ensures that the architecture remains maintainable and expandable in the long term.

With arc42, you can ensure that your software architecture is not only based on solid foundations, but is also documented in such a way that it remains understandable and accessible to all stakeholders - a decisive advantage in a constantly evolving technology world.

The individual areas of arc42 documentation

arc42 divides the documentation of a software architecture into several clearly defined areas. Each of these areas has a specific purpose and helps to document the architecture comprehensively and comprehensibly. In the following, we will look at the most important areas and explain why they are essential.

1. Introduction and objectives
Purpose: This section describes the motivation and overarching objectives of the system. It explains why the system is being developed in the first place and the key requirements it must fulfill.
Importance: A clear definition of the objectives is crucial to ensure that all stakeholders understand the direction of the project and that the architecture is aligned with it.

2. Constraints
Purpose: Constraints are the specifications and framework conditions that restrict or influence the architecture. These can be of a technical, organizational or legal nature. Examples include certain technologies that must be used, standards that must be adhered to or legal regulations that the system must fulfill.
Importance: Understanding and documenting constraints is crucial, as they can limit the freedom of architectural decisions and anticipate certain design decisions. They help to define the scope of the architecture and ensure that all requirements and regulations are met.

3. Contexts & Scope
Purpose: This section describes the various contexts of the system, how it interacts with external systems and which external interfaces exist.
Importance: Understanding the system contexts is important in order to recognize dependencies on other systems and their effects on your own architecture.

4. Solution strategy
Purpose: The solution strategy provides an overview of the basic technical and architectural approaches chosen to meet the requirements. It describes how the architecture will achieve the objectives and how the key challenges will be addressed.
Importance: A clearly formulated solution strategy is essential to ensure that all stakeholders understand and support the key architectural decisions. It serves as a guide for the more detailed elaboration of the architecture.

5. Building block view
Purpose: The building block view describes the internal structure of the system by showing the most important building blocks (modules, components) and their relationships to each other.
Importance: This view makes it possible to clearly understand the internal structures of the system and to ensure that the architecture remains scalable and maintainable.

6. Runtime view
Purpose: The runtime view shows how the system components interact at runtime and which communication flows exist between the components.
Importance: An understanding of the runtime view is essential for analyzing and optimizing system performance and identifying potential bottlenecks.

7. Deployment view
Purpose: This section describes how the various components of the system are physically distributed, for example on servers, cloud instances or devices.
Importance: The distribution view helps to understand the infrastructure requirements and ensure that the system runs efficiently and reliably in different environments.

8. Cross cutting concepts
Purpose: Cross cutting concepts include overarching concepts that run through different parts of the system and are not limited to a single component. This includes aspects such as security, error handling, logging, persistence, authentication and authorization, or even performance optimizations.
Importance: The documentation of these overarching concepts is important as it ensures that these central aspects of the system are implemented consistently and uniformly. A well thought-out cross-cutting concept can significantly improve the maintainability and expandability of the system and ensure that important requirements are taken into account system-wide.

9. Architecture decisions
Purpose: This section documents the important architectural decisions that were made and the reasons that led to these decisions.
Importance: The documentation of architectural decisions is crucial for traceability and makes it easier to make well-founded adjustments or extensions in the future.

10. Quality requirements
Purpose: The quality requirements for the system are described here, e.g. performance, security, reliability and maintainability.
Importance: Understanding the quality requirements is crucial to ensure that the architecture meets these requirements and that the system can be operated successfully in the long term.

11. Risk assessment and technical debt
Purpose: This section documents the potential risks and technical debt of the system, as well as strategies to mitigate them.
Importance: A conscious examination of risks and technical debt enables proactive measures to be taken to minimize negative effects on the project.

12. Glossary
Purpose: The glossary contains definitions and explanations of important terms used in the project.
Importance: A common understanding of terms and concepts is essential to avoid misunderstandings and ensure effective communication within the team.

The advantages of arc42: argumentation for its use

The use of arc42 offers numerous advantages that can significantly improve software projects. The most important reasons why arc42 should be used in every development project are listed below:

• Traceability and comprehensibility: arc42 ensures that all architectural decisions are clearly documented and comprehensible. This enables every team member to quickly familiarize themselves with the architecture, regardless of whether they were involved from the beginning or joined later. The uniform structure of arc42 promotes a common language within the team, which makes collaboration and understanding much easier.
• Maintainability and flexibility: Software projects are constantly evolving and the architecture needs to be adapted to new requirements. A well-documented architecture ensures that these changes can be implemented efficiently and without risk. arc42 offers a flexible documentation structure that makes it possible to plan and implement architectural changes without jeopardizing existing functionality.
• Efficient communication with stakeholders: The architecture of a software project is not only relevant for the development team, but also for customers, managers and other stakeholders. arc42 makes it possible to document the architecture in a way that is understandable for non-technical stakeholders. This promotes transparency and trust in the project and facilitates the communication of decisions and progress.
• Saving time and increasing efficiency: Using arc42 saves a lot of time, as the template provides a proven structure and methodology for documentation. There is no need to reinvent the wheel, allowing the focus to be placed on developing and improving the software. arc42 provides the tools to make documentation efficient while ensuring high quality.

Why arc42 is the best choice

arc42 is not the only tool for architecture documentation, but it is the best choice for several reasons:

• Proven framework: arc42 was developed by renowned software architects who have brought extensive practical experience to this template. It is based on best practices and has proven itself in a wide range of projects and industries.
• Flexibility and adaptability: Regardless of whether you are working on a small start-up project or a large corporate project, arc42 is flexible enough to adapt to specific requirements. The individual modules of the template can be used or adapted as required, making it suitable for a wide variety of projects and teams.
• Standardization and consistency: arc42 creates a standardized documentation structure that is consistent for everyone involved. This not only facilitates the maintenance and further development of the project, but also the induction of new team members. Standardized documentation leads to fewer misunderstandings and promotes efficient collaboration.
• Expandability and future-proofing: arc42 is designed to grow with the project. It enables step-by-step expansion and adaptation of the documentation, which is particularly invaluable for long-term projects. This means that the architecture remains well documented and easy to maintain in the future.

Call to action: Investment in the architecture

The decision to use arc42 in projects represents an investment in the future of software architecture. A well-documented architecture is the key to success - it not only makes the project more transparent and maintainable, but also ensures that it remains sustainable in the long term. arc42 should be used to take documentation to the next level and ensure that the project is still successful and scalable years from now.

Arc42 in action

DokChess is a sample project that demonstrates the use of the arc42 template to document a software architecture. It is a chess application whose architecture was structured and documented with the help of arc42. The project shows how the different areas of arc42 - from building blocks to runtime views to quality requirements - can be used in a real software project to create a clear, understandable and maintainable architecture.

For more information, you can view the project here: https://www.dokchess.de/

Conclusion

arc42 offers a structured, tried-and-tested and flexible method for documenting software architectures. The advantages are clear: traceability, maintainability, efficient communication and consistent, standardized documentation. The use of arc42 ensures that the architecture is not only optimally equipped for the current project, but also for future developments. An investment in arc42 is an investment in the sustainability and long-term success of software projects.

Resources & Sources

https://www.florian-lenz.io/blog/arc42-fur-ihre-softwarearchitektur-die-beste-wahl-fur-nachhaltige-dokumentation
https://dev.to/arc42/brief-introduction-to-arc42-1c0l
https://www.arc42.de/
https://entwickler.de/software-architektur/architekturdokumention-arc42-template
https://github.com/BrutalHack/Arc42AzureDevOpsWiki