# Connector Implementation Guide

## Connector Interface
Every external data connector should expose:
- `name`
- `capabilities`
- `is_configured()`
- `health_check()`
- `fetch_by_area(area_geometry, parameters)`
- `normalize(raw_result)`
- `cache_key(area, parameters)`

## Required Connectors
### GRB Connector
V1 target: fetch or register reference building polygons. If live WFS cannot be implemented immediately, build the interface and support fixture/local import honestly.

### OSM Connector
V1 target: fetch buildings/roads/water/green where possible using Overpass or local fixture fallback.

### Sentinel Connector
V2 target. In V1 it should remain disabled with clear roadmap state.

## Connector Failure Behavior
- timeout -> `CONNECTOR_TIMEOUT`
- missing config -> `CONNECTOR_UNCONFIGURED`
- invalid response -> `CONNECTOR_INVALID_RESPONSE`
- no data -> valid empty result, not error