loom

Forward schema description language. Weaves design intent into physical schemas.

loom is a TypeScript-implemented schema engine that takes a design schema (business identity, fields, value types, extension strategy) and projects it into physical schemas (SQL DDL, atlas-yaml/v2). It is the forward-direction complement to atlas-yaml/v2, which describes the physical fact of an existing database.

Status

Pre-alpha. Skeleton only — see docs/specs/2026-06-17-loom-design.md for the validated design specification.

Why loom?

• atlas-yaml/v2 describes what a database is (physical fact, diff-stable)
• loom-schema describes what a database should be (design intent, business identity, extension strategy)
• One-way projection: design → physical. Reverse is lossy and needs LLM/human assistance (loom lift)

See spec §"命名说明" for the etymology (loom = weaving machine; atlas = collection of maps).

Repository layout

loom/
  packages/
    core/        schema engine (pure TS, environment-agnostic)
    cli/         CLI entry point (thin wrapper over core)
  docs/
    specs/       design specifications

Quick start

pnpm install
pnpm build
pnpm test

# Run CLI directly
./packages/cli/bin/loom version

Design decisions

See docs/specs/2026-06-17-loom-design.md §2 for the full decision table. Highlights:

1. Two independent layers (loom design ↔ atlas physical), one-way projection
2. Sidecar EAV extension strategy — main tables never change shape for custom fields
3. system / module / {value_type | table | entity} file organization, base_types.yaml global type catalog
4. value types can map to multiple physical columns (Money = amount + currency)
5. YAML is the AST/IR — no second source of truth
6. loom fmt enforces diff-stable formatting

License

TBD.