Layer	Database	Grain	Owner
L1	`L1/L1.db`	One raw network capture per match	Import pipeline
L2	`L2/L2.db`	Normalized match, player, round and event facts	L2 Builder
L3	`L3/L3.db`	Roster features and profile marts	L3 Builder
Web	`Web/Web_App.sqlite`	Lineups, comments, jobs and editorial data	Flask app

Rules

Paths are defined only in database/paths.py.
Schemas live next to their owning database.
Builders may read the previous layer and write only their own layer.
User-generated Web data is never restored as part of an ETL rollback.
A full import must run through database/pipeline.py.
Pipeline runs are serialized by database/.pipeline.lock.
L1/L2/L3 are backed up before a full pipeline run.
Missing metrics are stored as NULL, not fabricated zero values.
Admin -> Data Integrity is the operational source of truth.
Web schema changes increment Config.WEB_SCHEMA_VERSION.
YRTV_DATA_DIR owns runtime databases; code schemas always stay in Git.
Container and production deployments must keep runtime data outside the image and source checkout.

Entry Points

make l1          # Import output_arena JSON into L1
make l2          # Rebuild normalized facts
make l3          # Rebuild active-roster features
make pipeline    # Run L1 -> L2 -> L3 with backup and validation
make check       # Compile and run tests
make bootstrap   # Initialize an empty runtime data root
make prepare-data # Copy legacy data into runtime-data

Directory Policy

Without YRTV_DATA_DIR, L1/, L2/, L3/, Web/ remain the compatible development runtime.
With YRTV_DATA_DIR, those folders provide code and schemas while databases live under the configured external directory.
backups/: generated rollback snapshots; ignored by Git.
schema_bkp/: historical schema research only; not used at runtime.
L1B/: reserved demo-parser integration; not used at runtime.
L3/Roadmap/: historical design notes; not used at runtime.

Large-scale directory moves are deliberately deferred until the legacy builders no longer depend on their current module layout.