Migration Engine (v0.1)

1. Purpose

The Migration Engine is responsible for:

• Validating migration definitions
• Ensuring migration compatibility with a ChangeSet
• Executing migrations deterministically
• Producing a transformed Canonical Graph

It operates after:

• Diff Engine
• Versioning Engine
• Validation Engine

It MUST NOT:

• Compute diff
• Re-classify version bump
• Mutate the source graph in place

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2. Conceptual Model

Migration execution is a transformation:

applyMigration(
    previousGraph: CanonicalGraph,
    migrationDefinition: MigrationPlan
): CanonicalGraph

The output MUST be a new Canonical Graph instance.

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3. Migration Preconditions

Before execution, the engine MUST verify:

1. Version bump is valid
2. Migration version matches declared version transition
3. Migration plan is complete
4. Migration operations are structurally valid

If any precondition fails → execution MUST abort.

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4. Migration Plan Model

A MigrationPlan MUST include:

MigrationPlan {
    fromVersion: SemVer
    toVersion: SemVer
    operations: OrderedCollection<MigrationOperation>
}

Operations MUST be executed in declared order.

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5. Migration Operation Types

Supported operation types MUST be explicitly enumerated:

• ADD_NODE
• REMOVE_NODE
• MODIFY_ATTRIBUTE
• RENAME_NODE
• TRANSFORM_VALUE
• ADD_EDGE
• REMOVE_EDGE

The allowed set MUST be stable and versioned.

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6. MigrationOperation Schema

MigrationOperation {
    type: OperationType
    targetPath: CanonicalPath
    parameters: object
}

Each operation type MUST define required parameters.

Example:

{
  "type": "MODIFY_ATTRIBUTE",
  "targetPath": "/processes/order/states/approved",
  "parameters": {
    "attribute": "label",
    "newValue": "Approved Order"
  }
}

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7. Execution Phases

Migration execution MUST occur in ordered phases:

1. Structural removals
2. Structural additions
3. Attribute modifications
4. Value transformations
5. Edge updates

This ordering ensures deterministic and conflict-free application.

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8. Determinism Requirements

The Migration Engine MUST:

• Execute operations in deterministic order
• Reject ambiguous operations
• Produce identical output for identical input and plan
• Guarantee stable canonicalization after execution

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9. Safety Guarantees

The engine MUST enforce:

• Target path existence before modification
• No duplicate node creation
• No orphan references
• No illegal structural states
• No partial commit (all-or-nothing behavior)

If any operation fails → entire migration MUST rollback.

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10. Atomicity

Migration MUST be atomic.

Implementation MAY:

• Build intermediate mutable graph
• Apply operations
• Validate final graph
• Freeze into new Canonical Graph

If validation fails → discard result.

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11. Integration with Validation Engine

After applying migration:

• The resulting graph MUST be canonicalized
• The Validation Engine MUST run
• Any validation error MUST invalidate migration

Migration success requires post-validation success.

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12. Compatibility with Diff Engine

Migration MUST be consistent with ChangeSet:

• All breaking changes MUST be addressed by migration operations
• No migration operation may contradict ChangeSet classification

If ChangeSet indicates breaking change but no migration addresses it → invalid.

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13. Idempotency

Migration execution MUST NOT be assumed idempotent.

However, the engine MUST detect:

• Reapplication of same migration
• Version mismatch

Reapplying a completed migration MUST fail.

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14. Version Transition Enforcement

MigrationPlan.fromVersion MUST equal previous version. MigrationPlan.toVersion MUST equal current version.

Mismatch MUST invalidate execution.

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15. Performance Expectations

Migration execution SHOULD operate in:

O(O + N)

Where:

• O = number of operations
• N = number of nodes

Lookup MUST use canonical path indexing.

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16. Conflict Detection

The engine MUST detect:

• Multiple operations targeting same node illegally
• Removal of node later modified
• Rename conflicts
• Edge creation pointing to non-existent nodes

Conflict detection MUST be deterministic.

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17. Logging and Audit

The engine MAY produce an execution log:

MigrationExecutionLog {
    operationsExecuted: number
    durationMs: number
    warnings: string[]
}

Logging MUST NOT alter behavior.

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18. Error Handling

Migration errors MUST include:

• Operation index
• Target path
• Error code
• Message

Errors MUST be deterministic.

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19. Non-Goals

The Migration Engine does NOT:

• Auto-generate migration plans
• Infer missing transformations
• Relax validation rules
• Partially apply operations

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20. Compliance Criteria

An implementation is compliant if:

• It enforces version transition consistency
• It applies operations atomically
• It guarantees determinism
• It validates post-migration graph
• It rejects inconsistent plans

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21. Summary

The Migration Engine:

• Applies declared transformations
• Guarantees atomic execution
• Enforces structural safety
• Integrates with validation and versioning
• Produces a new canonical graph