Rail — network operations & connectivity

The problem. A rail network is a web of stations joined by track segments. When a segment is closed — a fault, flooding, maintenance — the controller's first question is sharp and time-critical: is the line between two points still connected, or is it severed? If severed, trains must reroute or terminate now. That's a reachability question, and on a graph it's a single traversal.

This scenario introduces a graph pattern the others don't: connectivity — walk the network to see what's still reachable after a link goes down.

Set up demo data

New workspace? Run this once (Python) to create the rail network (stations joined by connects_to track) so the reachability check has a graph to walk. Safe to re-run.

import datahub_sdk

client = datahub_sdk.DataHubClient.from_env()

client.resources.create(
    [datahub_sdk.Resource(external_id=x, name=x, labels=[x]) for x in
     ["station_oslo_s", "junction_lierstranda", "station_drammen", "station_bergen_n"]],
    [datahub_sdk.RelForm.by_external_ids("station_oslo_s", "junction_lierstranda", "connects_to"),
     datahub_sdk.RelForm.by_external_ids("junction_lierstranda", "station_drammen", "connects_to"),
     datahub_sdk.RelForm.by_external_ids("station_drammen", "station_bergen_n", "connects_to")])

1. Model the network

Stations are resources; track segments are connects_to edges between them.

Java

List<RelForm> track = List.of(
    rel("connects_to", "station_oslo_s", "junction_lierstranda"),
    rel("connects_to", "junction_lierstranda", "station_drammen"),
    rel("connects_to", "station_drammen", "station_bergen_n"));

client.resources().create(stations, track);

Python

import datahub_sdk

track = [
    datahub_sdk.RelForm.by_external_ids("station_oslo_s", "junction_lierstranda", "connects_to"),
    datahub_sdk.RelForm.by_external_ids("junction_lierstranda", "station_drammen", "connects_to"),
    datahub_sdk.RelForm.by_external_ids("station_drammen", "station_bergen_n", "connects_to"),
]
client.resources.create(stations, track)

Rust

use dataplatform_rust_sdk::relations::RelForm;

let track = vec![
    RelForm::by_external_ids("station_oslo_s", "junction_lierstranda", "connects_to"),
    RelForm::by_external_ids("junction_lierstranda", "station_drammen", "connects_to"),
    RelForm::by_external_ids("station_drammen", "station_bergen_n", "connects_to"),
];
api.resources.create(stations, track).await?;

2. Is the line still connected?

A segment is closed — remove it (or exclude it), then ask: starting from one terminal, is the other terminal still in the reachable set? Walk connects_to from the origin and check whether the destination is among the returned nodes.

Java

RelatedResourcesForm reach = new RelatedResourcesForm();
reach.setExternalId("station_oslo_s");
reach.setDepth(100);
reach.setRelationshipTypes(List.of("connects_to"));

ResourceNetwork reachable = client.resources().fetchRelated(reach);

boolean stillConnected = reachable.nodes().stream()
    .anyMatch(n -> n.getExternalId().equals("station_bergen_n"));

System.out.println(stillConnected ? "route open" : "SEVERED — reroute required");

Python

reachable = client.resources.fetch_related(
    external_id="station_oslo_s", depth=100, relationship_types=["connects_to"])

still_connected = any(n.external_id == "station_bergen_n" for n in reachable.nodes)
print("route open" if still_connected else "SEVERED — reroute required")

Rust

use dataplatform_rust_sdk::resources::RelatedResourcesForm;

let reachable = api.resources.fetch_related(
    &RelatedResourcesForm::from_external_id("station_oslo_s")
        .with_depth(100)
        .with_relationship_types(vec!["connects_to".into()])).await?;

let still_connected = reachable.nodes().iter()
    .any(|n| n.external_id == "station_bergen_n");
println!("{}", if still_connected { "route open" } else { "SEVERED — reroute required" });

The returned node set is the connected component reachable from the origin. Membership answers connectivity directly — see Correlate alarms with the graph for the traversal mechanics.

3. Track punctuality

Dwell times and delays are series (station_drammen_dwell_s, service_r10_delay_min); roll them up for the punctuality report and raise a delay_threshold event when a service slips past its allowance.

See the result

With the network intact, the destination is reachable:

route open      ← station_bergen_n is in the set reachable from station_oslo_s

Delete a connects_to segment and re-run the check and it prints SEVERED — reroute required.

See also

• Model assets as a graph — modeling the network topology.
• Correlate alarms with the graph — reachability via traversal.
• Turn readings into events — punctuality alerts.