Seven parties. One line each may cross.

Three transit agencies and four mobility providers, under one regional authority. Each keeps local autonomy; each publishes through one adapter.

Inside every party's boundary sit three things. Operational systems: vehicles, counters, fare devices, chargers, which stay on the operational side of the OT and IT line. A local platform of whatever maturity the party has: a lakehouse like the agency platform on this site, or nothing more than a vendor export. And an adapter.

The adapter is the one thing the region asks for. It runs in the party's own account, maps vendor fields onto the regional contracts, applies the field classification, and drops restricted fields before anything leaves.

The names are placeholders. The design is meant to hold for any agencies that adopt it, not for one region.

Transit Agency A: Full stack: AVL, APC, AFC, GTFS, maintenance, charging
Transit Agency B: Same shape, different vendors, different maturity
Transit Agency C: Small: minimal adapter, no lakehouse
Bike share: Station status and trips (GBFS)
Ferry: Sailings, loads, a GTFS timetable
Ride-hailing: Pickups, drop-offs, wait times (MDS)
Scooters: Availability and trips (GBFS, MDS)

Coupling is constrained in one direction. Local operations never depend on the region. If the exchange is down, regional products degrade; no bus, gate or charger notices.