Temporal Versioning

Overview

Temporal Versioning treats every state change as immutable, creating a timeline of system states rather than mutations. It enables time travel, auditing, and historical analysis by maintaining a complete version history.

Key Concepts

• Version ID: Unique identifier for each version
• Delta Changes: Only store what changed between versions
• State Timeline: Linear or branching history of states
• Commit: The act of creating a new version
• Rollback: Reverting to a previous version

Benefits

• Time Travel: Inspect and revert to any previous system state
• Auditing: Every change is documented with its cause
• Analysis: Track how state evolves over time
• Concurrency: Simplifies concurrent operations with immutable states
• Debugging: Examine system state at any historical point

Implementation Considerations

• Storage Efficiency: Consider delta storage vs. full state copies
• Branching Strategy: Support for linear history vs. branched history
• Performance Impact: Balance history tracking with runtime performance
• Garbage Collection: Policy for pruning old versions
• Referential Integrity: Handling references between versioned objects

Core Interfaces

Versioned[S]
├── get_current_version_id() -> VersionId
├── get_version(version_id) -> S
├── commit(state, description) -> VersionId
└── get_history() -> List[VersionInfo]

Pattern Variations

Linear History

Simple version chain where each version has one parent and one child. Best for straightforward history tracking.

Branched History

Tree-like structure where versions can have multiple children. Useful for exploring alternative paths or concurrent editing.

Git-like Model

Sophisticated versioning with merge capability, allowing concurrent branches to be combined.

Integration with Other Patterns

• Reactive Event Mesh: Events can trigger version creation
• Perspective Shifting: Different views of version history
• State Projection: Projections built from version history
• Effect System: Version changes can be modeled as effects

Usage Examples

See the implementation file: nerv/temporal_store.md

Python Implementation

See the implementation code: nerv/python/temporal_store.py

Related Patterns

• Memento Pattern
• Command Pattern with History
• Event Sourcing
• Copy-on-Write