SQA-QC-Checklists/qc-erd.md

Quality Criteria: Entity Relationship Diagram (ERD)

Metadata

Key	Value
ID	QC-ERD-001
CrossReference	QC-DCD-001
DomainLanguages	IT Professional English

Version History

Date	Status	Author	Reviewer	Change	Commit
2026-10-01	Accepted	Jens Tirsvad Nielsen	S07	First public release (1.0.0)	—

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Purpose

The Entity Relationship Diagram specifies the persistent data structure that will back the system's Design Class Diagram, defining entities, keys, and relationships for storage. Its quality determines data integrity, query performance, and consistency between the design and the persisted data model.

Quality Criteria Checklist

Level: Mandatory criteria are the baseline every instance must meet; Optional criteria are advanced and may be deferred.

#	Criterion	Level	ISO/IEC 25010 Characteristic(s)	Notes
1	Primary keys (PK) identified for every entity	Mandatory	Functional Suitability, Reliability	Every entity must have a unique identifier
2	Foreign keys (FK) identified for every relationship requiring referential integrity	Mandatory	Functional Suitability, Reliability	Prevents orphaned or ambiguous references
3	Schema normalized to at least 3NF unless denormalization is explicitly justified for performance	Optional	Maintainability, Performance Efficiency	Justification must be documented in Notes when denormalized
4	Relationship cardinalities specified (1:1, 1:N, N:M) for every relationship	Mandatory	Functional Suitability	Missing cardinality is a common review-blocking defect
5	Data types consistent with corresponding Operation Contract/DCD attribute types	Mandatory	Compatibility, Maintainability	Prevents silent type mismatches between design and storage
6	N:M relationships resolved via explicit junction/associative entities	Mandatory	Functional Suitability	Required for correct relational representation
7	Naming conventions for entities/attributes are consistent and free of implementation-specific abbreviations	Optional	Usability, Maintainability	Improves readability and long-term maintainability

Common Defects

• Entities without a defined primary key
• Missing foreign keys on relationships that require referential integrity
• Unresolved N:M relationships without a junction entity
• Data types inconsistent with the DCD/Operation Contracts they implement
• Denormalization applied without documented performance justification

Traceability Rule

• Backward: Must trace to the Design Class Diagram checklist (QC-DCD-001), particularly persistent classes and their attributes/associations
• Forward: Feeds into physical database implementation (schema creation, migrations) — outside this project's scope and outside the QC checklist chain, but must remain consistent with it

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