ADR-0001: Architectural Decision Records Process and Format

Status

Accepted

Date

2025-02-27

Context

As we begin the development of the Rust Flow Framework, we need a consistent way to document architectural decisions. Architectural Decision Records (ADRs) provide a mechanism to document important architectural decisions, their context, and their consequences.

This project is starting with no existing ADRs, so we need to establish a process and format for creating and maintaining them. This ADR documents how we will create, format, and manage ADRs throughout the project lifecycle.

Decision

We will use Architectural Decision Records (ADRs) to document all significant architectural decisions in the Rust Flow Framework. The following guidelines will be followed:

ADR Creation and Process

  1. Numbering: ADRs will be numbered sequentially with a four-digit number prefix (e.g., 0001, 0002).
  2. Format: ADRs will be stored as Markdown files in the /docs/adrs/ directory.
  3. Naming Convention: ADR files will be named with their number and a kebab-case title, e.g., 0001-adr-process-and-format.md.
  4. Creation Timing: ADRs must be created before implementing any architectural decision, not after.
  5. Incremental Creation: ADRs can be created incrementally as decisions are made throughout the project.

ADR Content Structure

Each ADR will include:

  1. Title: A clear, descriptive title following the format "ADR-NNNN: Title"
  2. Status: One of:
  3. Proposed: Initial state when the ADR is first drafted
  4. Accepted: Approved for implementation
  5. Rejected: Declined, with reasons documented
  6. Superseded: Replaced by a newer ADR (with reference to the new ADR)
  7. Amended: Modified after implementation
  8. Date: The date the ADR was last updated
  9. Context: The problem being addressed and relevant background information
  10. Decision: The architectural decision that was made and the reasoning
  11. Consequences: The results of the decision, both positive and negative
  12. Alternatives Considered: Other options that were evaluated and why they were not chosen

ADR Lifecycle Management

  1. Review Process: ADRs will be reviewed before they are accepted.
  2. Amendments: Existing ADRs can be amended with additional information, but the core decisions should not be changed after implementation.
  3. Superseding: If a decision changes fundamentally, a new ADR should be created that supersedes the old one. The old ADR should be updated to reference the new one.
  4. Retrospective Updates: Consequences that were not anticipated can be added to ADRs after implementation to serve as a record for future reference.

ADR Index

An index of all ADRs will be maintained in /docs/adrs/README.md to provide a central reference point.

Consequences

Positive

  1. Improved documentation of architectural decisions
  2. Better understanding of why certain approaches were chosen
  3. Historical context for future contributors
  4. Clear process for proposing and evaluating architectural changes
  5. Living documentation that evolves with the project

Negative

  1. Additional overhead for documenting decisions
  2. Maintenance burden for keeping ADRs up-to-date
  3. Potential for ADRs to become outdated if not properly maintained

Alternatives Considered

No Formalized Documentation

  • Pros: Less upfront work, more flexibility
  • Cons: Loss of context over time, difficulty onboarding new contributors, inconsistent decision-making

Wiki-Based Documentation

  • Pros: Easier collaborative editing, more flexible format
  • Cons: Separation from source code, less versioning control, potential for unstructured content

Comments in Code

  • Pros: Close proximity to implementation
  • Cons: Limited space, difficult to get a holistic view, not suitable for decisions that span multiple files

We chose the ADR approach because it provides a structured, version-controlled way to document decisions that is closely tied to the codebase but separate enough to provide a comprehensive view of the architecture.