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REVERSIBILITY.md

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Reversibility Policy

eTMA Handler is designed with reversibility as a core principle.

Philosophy

Every operation that modifies data should be undoable. Tutors should be able to experiment with marking without fear of losing work.

Implemented Reversibility

Marking Operations

Operation Reversible Method
Grade assignment ✅ Undo/redo stack
Add feedback ✅ Undo/redo stack
Delete feedback ✅ Soft delete + undo
Bulk grade ✅ Transaction rollback

File Operations

Operation Reversible Method
Import .fhi ✅ Can re-import
Export .docx ✅ Non-destructive
Delete assignment ✅ Soft delete (30 days)
Clear database ⚠️ Backup required

Configuration

Operation Reversible Method
Change settings ✅ Config versioning
Reset to defaults ✅ Backup preserved

Technical Implementation

CubDB Append-Only

CubDB uses an append-only B-tree, meaning:

  • Old versions preserved until compaction
  • Point-in-time recovery possible
  • No data loss from crashes

Automatic Backups

config :etma_handler,
  auto_backup: true,
  backup_interval: :hourly,
  backup_retention: 7  # days

Undo Stack

  • In-memory undo/redo for session
  • Persistent history for important operations
  • Configurable history depth

Recovery Procedures

Accidental Deletion

  1. Check soft-deleted items: Settings → Trash
  2. Restore within 30 days
  3. After 30 days: restore from backup

Corrupted Database

  1. Application creates automatic backup on start
  2. Restore: etma_handler restore --backup latest
  3. Manual: Copy from ~/.local/share/etma_handler/backups/

Grade Rollback

  1. Edit → Undo for recent changes
  2. History → View for older changes
  3. Select point-in-time to restore

Limitations

Operations that are NOT reversible:

  1. Backup deletion - Backups older than retention are purged
  2. Database compaction - Old versions removed after compaction
  3. Export to student - Once sent, cannot be recalled

Best Practices

  1. Enable auto-backup (default: on)
  2. Review before bulk operations
  3. Use soft delete (default: on)
  4. Export periodically for external backup

Last updated: 2024-12-01