atelier/matrix/domain-coverage.md

Domain Coverage

Where each core principle applies across the domains. The complement to principles-matrix.md: the matrix maps domain → core; this maps core → domains.

Core Principle Coverage

Core Principle	Domains that derive from it	Count
C1 Correctness	All 11 (security, data, api, testing, performance, observability, errors, uiux, documentation, concurrency, devops)	Universal
C2 Clarity	uiux, api, data, testing, observability, errors, documentation, devops	8
C3 Simplicity	security, data, testing, performance, documentation, concurrency, devops	7
C4 Locality	testing, concurrency	2
C5 Reversibility	api, data, uiux, concurrency, devops	5
C6 Composability	api, security, observability, errors, documentation, concurrency	6
C7 Observability	api, data, testing, performance, observability, errors, devops	7
C8 Economy	security, testing, performance, observability, concurrency	5

Interpretation

• C1 Correctness is universal — every domain derives from it. This confirms C1 as the floor.
• C4 Locality is the narrowest (2 domains: testing independence, concurrency boundaries). Locality is inherently domain-specific; not a gap.
• C2 Clarity and C7 Observability are the next-most-derived, confirming they are cross-cutting concerns.
• C6 Composability appears in 6 domains — it is most relevant where parts combine (api, errors, observability, documentation, concurrency) and least relevant where the unit is monolithic.

Per-Domain Coverage

Domain	C-rules derived from	Notes
UI/UX	C1, C2, C3, C5, C7	User-facing; clarity + reversibility
API	C1, C2, C3, C5, C6, C7	Contracts; composability + stability
Security	C1, C3, C6, C7, C8	8/10 non-tradeable (promoted to C1)
Data	C1, C2, C3, C5, C7	Truth + migration safety
Testing	C1, C2, C3, C4, C7, C8	Independence (C4) is unique
Performance	C1, C3, C6, C7, C8	Economy + measurement
Observability	C1, C2, C6, C7, C8	Self-referential (P7 derives from C7)
Errors	C1, C2, C5, C6, C7	Errors as data + reversibility
Documentation	C1, C2, C3, C5, C6	Docs-as-code + living docs
Concurrency	C1, C3, C4, C5, C6, C7, C8	Broadest derivation; locality (C4) unique
DevOps	C1, C2, C3, C5, C7	Reproducibility + rollback

Gaps and Notes

• No domain derives from only one C-rule. The minimum is 4 (UI/UX: C1, C2, C3, C5, C7 — actually 5). Every domain is multi-rooted.
• Concurrency has the broadest derivation (7 C-rules) — it touches the most core concerns.
• UI/UX and API are the most user-facing; they emphasize C2 (Clarity) heavily.
• Security is the only domain with explicit non-tradeable declarations; this promotes 8 of its rules to C1-equivalent per core/conflict-resolution.md §6.