Architecture Decision Records (ADR)

What is an Architecture Decision Record (ADR)?

An Architecture Decision Record (ADR) documents significant architecture decisions made throughout a project, capturing the context, rationale, and consequences of each decision. This promotes transparency and provides a historical reference for future design considerations.

Purpose of ADRs

• Knowledge Management: Consolidates architectural knowledge and decisions.
• Collaboration: Enhances team communication by documenting discussions and outcomes.
• Clarity: Provides clear reasoning behind design choices, making it easier for new team members to understand past decisions.

Best Practices for Writing ADRs

1. Be Specific: Each ADR should address a single architectural decision. Avoid conflating multiple decisions into one record.
2. Document Context: Clearly explain the project’s context and relevant considerations that influenced the decision. Include team dynamics and priorities.
3. Rationale and Consequences: Describe the reasons for the decision, including pros and cons, and outline the implications of the decision for the project and

future architecture. 4. Immutable Records: Once an ADR is created, avoid altering it. Instead, create a new ADR to reflect any changes or updates. 5. Timestamp Entries: Include timestamps to track when each decision was made, especially for aspects that may evolve over time (e.g., costs, schedules). 6. Use Templates: Utilize established templates for consistency and completeness in documenting ADRs.

Versioning ADRs

• Track Changes: Each time an ADR is updated or a new version is created, increment the version number (e.g., v1.0, v1.1, etc.) to reflect changes clearly.
• Document Changes: Include a "Changelog" section in the ADR to summarize what has changed in each version. This can include updates to the rationale, context, or decision consequences.
• Maintain Clarity: Ensure the latest version is easily accessible while keeping older versions for reference. You might consider using a version control system (e.g., Git) to manage this effectively.

How to Start Using ADRs

1. Identify Decisions: Collaborate with your team to identify significant architecture decisions that need documentation.
2. Select a Tool: Choose a tool for documenting ADRs (e.g., markdown files in a Git repository, Google Docs, project management tools).
3. Create ADRs: For each decision, create an ADR file in the adr directory, following naming conventions (e.g., choose-database.md).

File Name Conventions

• Use a present tense imperative verb phrase.
• Separate words with lowercase letters and dashes.
• Use .md extension for markdown formatting.

Templates

Refer to the following templates for structuring your ADRs:

• Decision record template by Michael Nygard
• Decision record template by Jeff Tyree and Art Akerman
• MADR project templates

Teamwork Advice for ADRs

• Foster a culture of collaborative decision-making and ensure ADRs are seen as valuable tools rather than bureaucratic requirements.
• Consider using the term "decisions" instead of "ADRs" to encourage engagement.
• Maintain living documents by updating existing ADRs with new information rather than rewriting them.

For More Information

• Architectural Decision Wikipedia
• Markdown Architectural Decision Records
• Tools for working with ADRs

By following these guidelines, your team can effectively leverage ADRs to enhance architectural decision-making and project transparency while keeping a clear version history of all architectural decisions.