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acdl/skills/data.md
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Jon Chery 2c08c778a9 docs(P4): Atelier skills mapping — 9 skill files + index + BA.A extension (REQ-221, REQ-222)
REQ-221: skills/ directory with 9 Atelier-derived skill files mapped to the
BA.A citizen-developer catalog: api, security, data, testing, observability,
errors, devops, infrastructure-as-code, compliance. Each names the Atelier
source path, distills first-principles to the citizen-dev-relevant subset,
links to agent-checklist triggers, maps to BA.A 5-skill catalog.

REQ-222: docs/skills.md index (9-skill table, Atelier provenance, 8 core
principles C1-C8, consumption instructions, reference-only domains, excluded
domains). PROJECT.md BA.A decision extended with the Atelier-derived skill
catalog reference.

---ci---
project: acdl
phase: 4
milestone: v1.18
status: execute
requirements:
  covered: [REQ-221, REQ-222]
  partial: []
---/ci---
2026-08-06 15:11:12 +00:00

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1.5 KiB
Markdown

# Skill: Data
> **Atelier source:** `domains/data/` (first-principles + schema-design,
> migrations, indexing)
> **Core principles:** C1 Correctness, C4 Locality, C6 Composability
> **BA.A mapping:** web API, worker, scheduled job
> **Consumer:** read this before authoring a service with a database.
## First Principles (citizen-developer-relevant subset)
- **Schema reflects the domain, not the application.** Tables model
real-world entities, not ORM classes.
- **Constraints are in the schema.** NOT NULL, UNIQUE, FK — the database
enforces integrity, not the application.
- **Migration has an `up` and a `down`.** Every migration is reversible.
- **Types are domain-accurate.** UUID for IDs, TIMESTAMPTZ for timestamps,
DECIMAL for money — not string/integer/everything.
- **No `SELECT *`; no N+1.** Explicit columns; eager-load relations.
## Agent-Checklist Triggers (§ Data)
- Schema reflects the domain (not the application)
- Constraints are in the schema (NOT NULL, UNIQUE, FK)
- Migration has an `up` and a `down`
- Types are domain-accurate (UUID, TIMESTAMPTZ, DECIMAL for money)
- No `SELECT *`; no N+1
## How Nova Uses This
Nova deploys your infrastructure (RDS, DynamoDB) but does not author your
schema. The data skill ensures the schema you bring meets production-grade
standards. The submission-readiness gate checks that your contract declares
the infrastructure; the data skill checks that the application running on
that infrastructure uses the database correctly.