pi-skill/skills/references/type-er.md

ER / Data Model

Best for: database schemas, API resource relationships, domain models.

Layout conventions

• Each entity is a two-section box:
  • Header: type tag (ENTITY) + entity name in Geist.
  • Body: field list in Geist Mono, one per line. PK prefixed with #, FK prefixed with →.
• Relationships: lines between entities with cardinality at each end:
  • 1, N, 0..1, 1..* in Geist Mono, 8px, placed 10–12px from the entity edge.
  • Optional relationship label ("has", "belongs to") centered on the line.
• Group related entities close; lay out so most relationships are straight lines, not tangles.
• Coral on the aggregate root or central entity of the model.

Anti-patterns

• Drawing an arrow for every FK on a model with dozens — lay out by cluster instead.
• Inconsistent cardinality notation between ends of the same relationship.
• Fields padded to equal-height boxes — natural height by content is fine.

Examples

• assets/example-er.html — minimal light
• assets/example-er-dark.html — minimal dark
• assets/example-er-full.html — full editorial