S4: Setback Compliance — Clermont-Ferrand

Beginner CLI + Map

Capabilities: filter

Use Case

An urban-planning team wants to illustrate the L111-6 setback rule on Clermont-Ferrand's structural axes (importance 1 and 2 — motorways and national roads). The pipeline collapses to a single step: extract the target network. The whole point of the scenario lives downstream — a planner sketches a building project (polygon or point) on the map and immediately sees whether the setback is honoured, via a server-side DML trigger backed by a client-side gradient.

IGN BD TOPO V3 Data

Layer	Content	Features	Key attributes	Source
routes	BD TOPO road segments	2,272	nature, importance, nom_1_gauche	data.geopf.fr — BDTOPO_V3:troncon_de_route
batiments	BD TOPO building footprints	~800	usage_1, hauteur	data.geopf.fr — BDTOPO_V3:batiment

python examples/prepare_playground_data.py --city clermont-ferrand
gispulse info examples/datasets/clermont_ferrand_bdtopo.gpkg --layer routes

Pipeline (1 step)

routes ──► filter (importance ∈ {1,2})              # keep only motorways + national roads

Why a single step?

S4 is about the declarative rule + reactive DML trigger combo. Computing length or cost would be filler: the focus is on the live setback evaluation, not on a batch job.

Rules

{
  "version": 2,
  "steps": [
    {
      "id": "filter_major_roads",
      "capability": "filter",
      "params": { "expression": "importance in ['1','2']" }
    }
  ]
}

Download

scenario-4-rules.json

Execution

gispulse run examples/datasets/clermont_ferrand_bdtopo.gpkg \
  --layer routes \
  --rules playground/scenario-4-rules.json \
  -o output/structural_network.gpkg

gispulse serve output/structural_network.gpkg

DML Trigger — Setback Compliance Check

We attach a DML trigger on the batiments layer: every INSERT is evaluated against two predicates (geometric + attribute). If the building is residential and within 250 m of a structural road (importance 1-2 — motorways and national roads), the cascade fires.

The overlay precomputes 5 concentric rings (50 / 100 / 150 / 200 / 250 m) around that network. They are a UX gradient: the client picks the smallest ring a drawn feature touches and assigns the matching tier color, no server round-trip. The backend trigger remains a single geometric predicate at buffer_m: 250.

{
  "name": "alert_road_setback_violation",
  "event": "FEATURE_CREATED",
  "trigger_type": "DML",
  "category": "BUSINESS_RULE",
  "severity": "warning",
  "conditions": {
    "table": "batiments",
    "operations": ["INSERT"]
  },
  "predicates": [
    {
      "type": "geom",
      "op": "intersects",
      "ref_table": "routes",
      "ref_filter": "importance in ('1', '2')",
      "buffer_m": 250
    },
    { "type": "attr", "field": "usage_1", "op": "eq", "value": "Residentiel" }
  ],
  "predicate_logic": "AND",
  "actions": [
    { "action_type": "FLAG_FEATURE", "config": { "field": "_safety_alert", "value": "ROAD_SETBACK_VIOLATION" } },
    { "action_type": "LOG_EVENT", "config": { "message": "Residential building within 250 m of a structural road (importance 1-2) - check L111-6 setback rule", "level": "warning" } },
    { "action_type": "NOTIFY", "config": { "message": "URBA ALERT: new residential building within 250 m of a structural road (motorway or national) in Clermont-Ferrand. Check L111-6 setback rule.", "channel": "urbanisme" } }
  ],
  "enabled": true
}

Download

scenario-4-trigger.json — inspired by French Code de l'urbanisme L111-6 (75 m motorway / 25 m major traffic setback). The importance in ('1','2') filter sticks to the actual L111-6 scope (top-tier axes); the buffer_m: 250 radius is widened from the legal text so the alert reads at the metro-area zoom.

Architecture

INSERT batiments -> DML Trigger
                     |
                     +- GeomPredicate : intersects(buffer(routes WHERE importance in (1,2), 250 m)) OK
                     +- AttrPredicate : usage_1 == 'Residentiel' OK
                     |
                     v MATCH -> 3-action cascade
                     +- FLAG_FEATURE -> _safety_alert = ROAD_SETBACK_VIOLATION
                     +- LOG_EVENT    -> warning logged
                     +- NOTIFY       -> urbanisme channel

Client (UX) : 5 precomputed rings 50/100/150/200/250 m
              -> drawn feature (polygon OR point) coloured by closest ring it touches
              -> red <= 200 m | orange 200-250 m | green > 250 m

Interactive playground

The map shows the 5 concentric rings (50 / 100 / 150 / 200 / 250 m) around importance 1-2 roads as a red→orange gradient, precomputed by build_playground_data.py → setback_zone.geojson.gz.

Draw mode — pick from the toolbar:

• Polygon: sketch a mock building footprint (seeded with usage_1 = "Residentiel"). The geometric test checks the full polygon-against-rings intersection.
• Point: drop a siting marker. The test picks the tier of the ring that contains the point.

In both cases the client keeps the smallest distance_m (= the closest road) and applies:

• tier ≤ 200 m → dark red feature (#7F0000), FLAG_FEATURE / LOG_EVENT / NOTIFY cascade fires, severity warning
• only the 250 m ring (200 < d ≤ 250 m) → orange feature (#E65100), cascade fires, WARNING tier flagged in the panel
• no ring intersects (> 250 m) → green feature (#2E7D32), NO MATCH: polygon outside setback zone (> 250 m)
• inside the zone but usage_1 ≠ Residentiel → tier color kept, NO MATCH, attribute predicate KO

Everything runs in-browser: drawings accumulate in local drawn_batiments_polys / drawn_batiments_pts layers (colorField: '_style_color'); the alert_road_setback_violation trigger is loaded from scenario-4-trigger.json and evaluated (rings + attr predicates) client-side — same intent as the server's TriggerEvaluator, no network round-trip per draw.

Try it live

Live Demolists available capabilities (starting with filter) used by the S4 pipeline

GET/capabilities

Live Demolists demo datasets, including clermont_ferrand_bdtopo loaded for this scenario

GET/datasets

Next steps

• S3: Accessibility — isochrones on the same network
• Vector capabilities — filter and the rest
• FTTH template — complete fiber design pipeline (connectivity, shortest_path, allocation)