# Canonical Schema

> A formal definition of one concept's shape, published once and used by every API, message and store that carries the concept.

Record: `architecture:canonical-schema`
Kind: artifact
Layer: [Contracts Core](https://banes-lab.com/records/layer/contracts-core.md)
Severity: recommended
Scope: data, message, API
Canonical: https://banes-lab.com/ontology#architecture-canonical-schema

Listed in [Architecture principles](https://banes-lab.com/api/records/architecture.md), after [Canonical Data Model](https://banes-lab.com/records/architecture/canonical-data-model.md) and before [Canonicalization](https://banes-lab.com/records/architecture/canonicalization.md).

## Repair

- Refactored by: Align Schema, Add Versioned Schema
- Detected by: schema diff conflict
- Violated by: divergent schemas for same concept
- Measured by: schema reuse/conformance rate
- Enforced by: schema registry

## Requires

- [Canonical Data Model](https://banes-lab.com/records/architecture/canonical-data-model.md)

## Reinforces

- [Schema Contract](https://banes-lab.com/records/architecture/schema-contract.md)

## Enables

- [Schema Validation](https://banes-lab.com/records/architecture/schema-validation.md)

## Conflicts with

- [Schema Drift](https://banes-lab.com/records/architecture/schema-drift.md)

## In tension with

- [Service-Specific Schemas](https://banes-lab.com/records/lexicon/service-specific-schemas.md)

## Tensions

- [Canonical Schema / Service-Specific Schemas](https://banes-lab.com/records/tension/canonical-schema-service-specific-schemas.md)

## Severity

- [recommended](https://banes-lab.com/records/vocabulary/severity-recommended.md)

## Category

- [Schema / Canonical Data / Semantics](https://banes-lab.com/records/architecture-category/schema-canonical-data-semantics.md)

## Linked from

- [Anti-patterns](https://banes-lab.com/ontology/principles/architecture-category-anti-patterns.md)
- [Contracts / Interfaces / Compatibility](https://banes-lab.com/ontology/principles/architecture-category-contracts-interfaces-compatibility.md)
- [Schema / Canonical Data / Semantics](https://banes-lab.com/ontology/principles/architecture-category-schema-canonical-data-semantics.md)
- [Schema / Canonical Data / Semantics](https://banes-lab.com/ontology/lexicon/lexicon-category-schema-canonical-data-semantics.md)
- [Severity levels](https://banes-lab.com/ontology/schema/the-vocabulary-severity.md)
- [The resolutions](https://banes-lab.com/ontology/schema/the-resolutions.md)