# Data Mesh Contract Quick Guide > **Guide Origin**: Official | **ArcKit Version**: [VERSION] `/arckit:data-mesh-contract` creates federated data product contracts for mesh architectures with SLAs, governance, and interoperability guarantees. --- ## Inputs Checklist | Artefact | Purpose | |----------|---------| | `ARC--DATA-v1.0.md` with entity definitions | Provides schema source of truth | | `ARC--REQ-v1.0.md` with DR-xxx entries | Defines data quality requirements and SLAs | | `ARC--STKE-v1.0.md` | Identifies domain owners and data consumers | | Architecture principles | Ensures mesh alignment with governance standards | --- ## Command ```bash /arckit:data-mesh-contract Create contract for data product ``` Output: `projects//ARC--DMC-001-v1.0.md` (uses multi-instance numbering) --- ## What is a Data Mesh Contract? A **data product contract** defines the formal agreement between a data product provider (domain team) and consumers in a federated mesh architecture. Unlike traditional data models, mesh contracts emphasize: - **Federated ownership** – Domain teams own their data products end-to-end - **Data as a product** – Treated like APIs with SLAs, versioning, and support - **Self-serve infrastructure** – Standardized access patterns and discovery - **Computational governance** – Automated policy enforcement --- ## Deliverable Snapshot | Section | Highlights | Next Action | |---------|------------|-------------| | Product metadata | Domain, owner, mesh plane alignment | Assign product owner and steward | | Schema & versioning | Contracted fields, breaking change policy | Sync with `ARC--DATA-v1.0.md` for consistency | | SLAs | Freshness, availability, quality KPIs | Define monitoring thresholds in observability platform | | Access methods | APIs, query endpoints, data feeds | Document authentication and rate limits | | Data quality | Validation rules, testing requirements | Implement automated quality checks | | Governance & policy | GDPR compliance, access controls, audit hooks | Review with DPO; integrate with governance platform | | Consumer obligations | Usage constraints, attribution, support SLA | Publish in data catalogue for discovery | | Change management | Versioning, deprecation, approval workflow | Establish governance board review cadence | --- ## UK Government Context ### Technology Code of Practice Alignment | TCoP Point | Mesh Contract Application | |------------|---------------------------| | **8. Share, reuse and collaborate** | Federated data products replace siloed databases | | **6. Make things secure** | Access policies and encryption enforced at contract level | | **7. Make privacy integral** | PII classification, consent management, and data subject rights | | **11. Define your purchasing strategy** | Reuse existing mesh products before building new ones | ### Data Quality Framework Mesh contracts support the **Government Data Quality Framework** five dimensions: 1. **Accuracy** – Validation rules and quality KPIs in contract 2. **Validity** – Schema constraints and allowed values 3. **Completeness** – Mandatory field requirements and null handling 4. **Consistency** – Cross-system reconciliation rules 5. **Timeliness** – Freshness SLAs and update frequency ### National Data Strategy (NDS) Contracts align with NDS pillars: - **Pillar 1 (Unlocking value)** – Discoverability and self-serve access - **Pillar 2 (Secure and resilient infrastructure)** – Security controls in contract - **Pillar 3 (Transforming capability)** – Federated domain expertise - **Pillar 4 (Ensuring responsible use)** – Governance and ethics policies --- ## Mesh Architecture Principles ### Domain-Driven Design - Each contract represents **one domain's data product** - Domain teams own product lifecycle (schema, SLA, support) - Cross-domain data sharing via published contracts ### Data Product Characteristics - **Discoverable** – Registered in data catalogue with metadata - **Addressable** – Unique endpoint or data lake path - **Understandable** – Schema, semantics, and lineage documented - **Trustworthy** – SLAs, quality metrics, and governance - **Secure** – Access policies and encryption standards - **Interoperable** – Standard formats and protocols ### Federated Computational Governance - **Automated policy enforcement** – Not manual review - **Global standards** – Applied locally by domain teams - **Observable compliance** – Auditable governance hooks --- ## Integration with ArcKit Workflow ### Prerequisites (Run These First) 1. `/arckit:principles` – Establish architecture principles including mesh standards 2. `/arckit:stakeholders` – Identify domain owners and consumers 3. `/arckit:data-model` – Define entities that become data products 4. `/arckit:requirements` – Capture DR-xxx data requirements including quality/SLAs ### Mesh Contract Generation 5. `/arckit:data-mesh-contract` – Create contract per domain data product ### Follow-Up Commands 6. `/arckit:traceability` – Link contracts to requirements and consumers 7. `/arckit:analyze` – Score contract completeness and governance quality 8. `/arckit:dpia` – If contract involves PII (auto-references contract) --- ## Compliance Focus ### GDPR / UK GDPR - **PII inventory** – List all personal data fields in contract - **Legal basis** – Document lawful basis for processing - **Data subject rights** – Mechanism for access, rectification, erasure - **Cross-border transfers** – If data leaves UK, document adequacy decisions - **Retention** – Contract specifies deletion policy ### Security Standards - **Encryption** – At-rest and in-transit standards - **Access control** – Role-based or attribute-based policies - **Audit logging** – Who accessed what data when - **Threat model** – Known risks and mitigations --- ## Contract Lifecycle ### 1. Design Phase - Domain team drafts contract using template - References source `ARC--DATA-v1.0.md` for schema - Defines SLAs based on consumer requirements - Documents governance policies ### 2. Review Phase - Architecture review against mesh principles - DPO review for privacy compliance - Security review for access controls - Governance board approval (if required) ### 3. Publishing Phase - Register contract in data catalogue - Provision infrastructure (APIs, storage, monitoring) - Document consumer onboarding process ### 4. Operations Phase - Monitor SLA adherence (freshness, availability, quality) - Track usage metrics and consumer feedback - Respond to support requests per contract SLA ### 5. Change Management - Propose schema changes with impact analysis - Versioning strategy (semantic versioning recommended) - Deprecation notice period (e.g., 90 days) - Consumer migration support --- ## Review Tips - **One contract per domain data product** – Don't bundle unrelated datasets - **Start with high-value products** – Focus on data with multiple consumers - **Automate quality checks** – Contract is meaningless without observability - **Version early** – Use semantic versioning from day one (v1.0.0) - **Consumer feedback loop** – Review SLAs quarterly based on actual usage - **Federated ownership** – Domain team owns contract, not central data team --- ## Common Pitfalls ❌ **Treating contracts as documentation** – They must be enforceable via automation ✅ **Integrate with governance platform** – Use contracts to drive policy engines ❌ **Overly rigid schemas** – Allow for evolution with backward compatibility ✅ **Semantic versioning** – Breaking changes increment major version ❌ **Vague SLAs** – "High quality" is not measurable ✅ **Specific KPIs** – "99.5% availability, <5min freshness, >95% completeness" ❌ **Centralized approval** – Defeats federated mesh model ✅ **Guardrails + autonomy** – Global policies, local implementation ❌ **No consumer onboarding** – Great product, no users ✅ **Self-serve discovery** – Catalogue, examples, sandbox environment --- ## Related Commands - `/arckit:data-model` – Define entities before creating contracts - `/arckit:requirements` – Capture DR-xxx requirements that drive SLAs - `/arckit:traceability` – Link contracts to requirements and consumers - `/arckit:analyze` – Score contract completeness - `/arckit:dpia` – Privacy impact assessment for PII-containing products --- ## References - **PayPal Data Contract Template**: https://github.com/paypal/data-contract-template - **Open Data Contract Standard (ODCS)**: https://github.com/bitol-io/open-data-contract-standard - **Data Mesh book (Zhamak Dehghani)**: O'Reilly 2022 - **UK Government Data Quality Framework**: https://www.gov.uk/government/publications/the-government-data-quality-framework - **National Data Strategy**: https://www.gov.uk/government/publications/uk-national-data-strategy - **GovS 005: Data Standards**: https://www.gov.uk/government/publications/open-standards-for-government