Reference
Glossary
All technical terms used in this documentation, briefly explained and grouped by topic. Use the browser search (Ctrl+F) to find a term quickly.
Node-RED and operation
| Term | Meaning |
|---|---|
| Admin endpoint (adminAuth) | HTTP route that a node registers in the Node-RED editor, for example to load station lists or run test queries for the edit dialog. Admin endpoints are protected by the editor login (adminAuth). |
| Catch node | Standard node that catches errors reported by other nodes so flows can react to them, for example with a notification. |
| Change node | Standard node that sets, moves, renames or deletes message properties. Useful for adjusting payloads before a builder node. |
| Credentials | Encrypted credentials of a node, such as passwords or API keys. They are excluded when flows are exported. |
| Debug mode | Option of many nodes in this library that writes verbose logs as warnings to the debug sidebar. Enable it for troubleshooting only, because complete messages are logged as well. |
| Debug node | Standard node that shows messages in the debug sidebar. Useful for checking the output of a node. |
| Deploy | Button in the editor that activates changed flows. New or changed nodes only run after a deploy. |
| Event-based | Mode of a node without input that emits messages on its own as soon as data arrives, for example via an MQTT subscription. |
| Flow | A tab in the Node-RED editor with connected nodes. Flows are activated with Deploy and can be exported and imported as JSON. See First steps. |
| Flow context | Storage that applies within one flow only. See Context. |
| Function node | Standard node in which you apply JavaScript to a message. Several nodes of this library offer embedded transformation scripts that work similarly. |
| Global context | Storage that applies to the whole Node-RED instance. Some nodes keep caches there, for example feed entries already processed. |
| HTTP In node | Standard node that exposes an HTTP endpoint in Node-RED. Used, for example, as the target of subscription notifications. |
| Inject node | Standard node that creates a message manually or on a schedule. Most Data Connectors are triggered by an Inject node. |
| Context (context storage) | Storage that keeps values across messages. There is node, flow and global context. With a persistent context store the values survive a restart. |
Message (msg, payload) | The JavaScript object that travels between nodes. Data lives in msg.payload; further properties such as msg.topic control nodes. |
| Node | A building block in Node-RED with a clearly defined task. Nodes receive messages at the input and send messages at one or more outputs. |
| Node type | Technical name under which a node is registered in Node-RED, for example pegelonline or ngsi-builder. It appears in exported flows in the type field. |
| Palette (palette manager) | The list of available nodes on the left of the editor. Additional packages are installed via the palette manager. See Installation. |
| Polling | Querying a source regularly at fixed intervals, either via an Inject node or via an interval configured in the node. |
| Proxy (HTTPS_PROXY, NO_PROXY) | Intermediate server for outgoing connections in corporate networks. Node-RED and the nodes evaluate the environment variables HTTPS_PROXY, HTTP_PROXY and NO_PROXY. See Installation. |
| settings.js (httpNodeAuth) | Central configuration file of Node-RED. Among other things, it configures context storage, editor login and protection of HTTP endpoints (httpNodeAuth). |
| Status | Small indicator below a node with colour, shape and text, for example a green dot with the number of loaded records or a red ring on errors. |
| Timeout | Maximum time to wait for the response of an external service. Afterwards the node reports an error. |
| Topic | The msg.topic property of a message. With MQTT it names the channel; other nodes use it to tag or filter messages. |
| Trigger-based | Mode of a node that only fetches data when it receives a message at its input. The preceding Inject node determines the polling frequency. |
| Typed input | An input field whose value can come from different sources: fixed text, number, msg property, flow or global context, environment variable or JSON. |
| Environment variable (env, placeholder) | Value provided by the operating system or Node-RED that can be used in fields as type env or as a placeholder such as ${STELLIO_API_URL}. This keeps URLs and keys out of the flows. |
| User-Agent | HTTP header with which a client identifies itself to a service. Services such as Nominatim require a meaningful User-Agent. |
NGSI-LD and context broker
| Term | Meaning |
|---|---|
| @context (JSON-LD context, context URL) | JSON-LD context that maps the attribute names of an entity to unambiguous terms. The nodes set the context to match the Smart Data Model used. |
| Attribute | Property of an entity. NGSI-LD distinguishes Property, GeoProperty and Relationship. |
| Batch operation (batch upsert, batch delete) | NGSI-LD operation that creates, updates or deletes several entities in one request. |
| Context broker | Server component that stores NGSI-LD entities, makes them queryable and notifies subscribers about changes. In the Urban Data Space Platform this is Stellio. |
| Entity | Digital representation of a real-world object in NGSI-LD, for example a weather station. An entity has a URN identifier, a type and attributes. |
| Entity type | The type of an entity, for example WeatherObserved or Device. It determines which data model applies and can be queried from the broker. See Stellio Types. |
| ETSI (ETSI CIM) | European Telecommunications Standards Institute. Its group ISG CIM standardises NGSI-LD. |
| GeoProperty | Attribute with a geometry as GeoJSON, usually location with a point made of longitude and latitude. |
| JSON-LD | JSON for Linked Data. JSON format with a context that maps keys to unambiguous identifiers. NGSI-LD is built on it. |
| Link header | HTTP header with which broker queries specify the JSON-LD context. Determines whether type and attribute names are returned short or as full URIs. |
| NGSI-LD | API and data representation for context information standardised by ETSI, based on JSON-LD. Foundation of data exchange in the Urban Data Space Platform. See Typical data flow. |
| NGSI-v2 | Predecessor of NGSI-LD without JSON-LD context. Some sources still deliver data in a format modelled on NGSI-v2. |
| Notify URL (notification) | Address to which the broker sends the notifications of a subscription, for example an HTTP In node in Node-RED or QuantumLeap. |
| observedAt | Metadata of a property stating the observation time of a value in ISO 8601 format. |
| Property | Attribute of an entity with a value, for example temperature with the value 18.7. May carry metadata such as observedAt and unitCode. |
| q filter (query filter) | Filter expression in NGSI-LD queries that restricts entities by attribute values, for example temperature greater than 20. See Stellio Entities. |
| Relationship | Attribute that refers to another entity, for example refDevice pointing to a device. |
| Results count | HTTP header NGSILD-Results-Count with which the broker returns the total number of matches of a query. |
| Scope | Optional hierarchical classification of an entity in NGSI-LD, for example by organisation or area. |
| Subscription | Subscription to changes of certain entities. The broker sends notifications to a configured URL, for example an HTTP In node. See Stellio Create Subscription. |
| Tenant (NGSILD-Tenant, data space) | Logically separated data space in the context broker, addressed via the HTTP header NGSILD-Tenant. |
| unitCode | Metadata of a property with the unit of measurement as a UN/CEFACT code, for example CEL for degrees Celsius or MTR for metres. |
| Upsert | Write operation that creates an entity if it is missing and updates it otherwise. Post to Stellio works this way. See Post to Stellio. |
| URN (entity ID, ID prefix) | Unique identifier of an entity following the pattern urn:ngsi-ld:Type:identifier, for example urn:ngsi-ld:WeatherObserved:station-001. |
Platform and tools
| Term | Meaning |
|---|---|
| APISIX (API gateway) | API gateway of the Urban Data Space Platform. It publishes interfaces such as NGSI-LD or the CSV endpoint externally and protects them, for example with API keys. |
| Data Connector | Node of this library that fetches data from an external source and brings it into the flow. See Data Connectors. |
| Data Operation | Node of this library that processes or publishes data, for example NGSI-LD Builder or Post to Stellio. See Data Operations. |
| Dashboard | Visualisation of platform data, in the Urban Data Space Platform for example with Grafana or Apache Superset. |
| EUPL 1.2 (licence) | European Union Public Licence, version 1.2. Open-source licence under which all packages of the library are published. See About the project. |
| FIWARE | Open-source initiative for smart city platforms. Co-founder of the Smart Data Models and origin of the NGSI interfaces. |
| Open data (Datenlizenz Deutschland) | Freely usable data under an open licence, for example the German data licence dl-de/by-2-0. Many sources of this library are open data. |
| QuantumLeap | FIWARE component that stores notifications of a context broker as time series in a database. Typical target of a notify URL. |
| Smart Data Models (SDM) | Open, agreed data models for smart city objects, maintained by FIWARE, TM Forum, IUDX and OASC. The nodes of this library follow these models. |
| Stellio | Open-source context broker for NGSI-LD that stores current state data in the Urban Data Space Platform. Target of the Stellio nodes of this library. See NGSI-LD and Stellio. |
| Urban Data Space Platform (UDSP) | Open-source data platform by HYPERTEGRITY AG for municipalities. Node-RED is its component for data integration. |
| Utility node | Helper node of this library for cross-cutting tasks such as geocoding, spatial assignment or MQTT debugging. See Utility. |
Data models
| Term | Meaning |
|---|---|
| AirQualityForecast | Smart Data Model for air quality forecasts with a validity period. Output 2 of the Luftdaten node. |
| AirQualityObserved | Smart Data Model for air quality measurements such as particulate matter (PM10, PM2.5) and nitrogen dioxide. See Luftdaten node. |
| BikeHireDockingStation | Smart Data Model for rental stations of shared bikes and scooters. Target model for GBFS station data. |
| Device | Smart Data Model for a device, for example a LoRaWAN sensor. The Device Info node creates entities of this type. See Device Info. |
| EVChargingStation | Smart Data Model for charging stations with location, connector types and availability. See Open Charge Map. |
| FloodMonitoring | Smart Data Model for flood monitoring with water level and alert levels. |
| GreenspaceRecord | Smart Data Model for measurements in green spaces, such as soil moisture and soil temperature. |
| GtfsAgency, GtfsRoute, GtfsStop, GtfsTrip, GtfsStopTime | Smart Data Models of the Urban Mobility domain that map the tables of a GTFS timetable to entities: transit agencies, routes, stops, trips and stop times. See GTFS node. |
| NewsObserved | Model for news and announcements modelled on the Smart Data Models, with title, introduction, publication time and link. |
| OsmFeature | Output type of the Overpass node: one flat object per OpenStreetMap element with location and the OSM tags as attributes. |
| PointOfInterest | Smart Data Model for places of interest such as sights, facilities or services. |
| UVIndexObservation, UVIndexForecast | Output types of the OpenUV node for the current UV index and the hourly UV forecast, structured according to the conventions of the Smart Data Models. |
| Vehicle | Smart Data Model for vehicles, for example free-floating rental bikes (GBFS) or vehicle positions from GTFS Realtime. |
| WaterObserved | Smart Data Model for water body observations such as water level and discharge. |
| WeatherAlert | Smart Data Model for official weather warnings with severity, category and validity. |
| WeatherForecast | Smart Data Model for weather forecasts with a validity period. |
| WeatherObserved | Smart Data Model for current weather observations such as temperature, humidity, wind and precipitation. |
Data sources and services
| Term | Meaning |
|---|---|
| dataCycle (Datahub Rheinland-Pfalz) | Software for data hubs on which the Datahub Rheinland-Pfalz is based. Its API v4 delivers content such as points of interest, events and tours. See Datahub RLP node. |
| DELFI (gtfs.de) | German association for integrated passenger information that provides nationwide GTFS timetable data, for example via gtfs.de. |
| DWD (Deutscher Wetterdienst) | German Weather Service. Provides forecasts (MOSMIX) and official warnings via its open data server. See Weather package. |
| EDIS (EDIS MQTT) | MQTT broker of the German Federal Waterways and Shipping Administration through which Pegelonline distributes readings in real time. |
| Endress+Hauser Netilion | IIoT platform by Endress+Hauser for sensor data such as water level and soil moisture. Access via user account and API key. |
| Hochwasserportal NRW | Portal of LANUK with water levels and flood information for North Rhine-Westphalia. |
| LANUK | State Agency for Nature, Environment and Climate of North Rhine-Westphalia. Operates the Hochwasserportal NRW. See LANUK node. |
| MobilityData | Non-profit organisation that maintains the GTFS, GTFS Realtime and GBFS specifications. |
| Nivus DataKiosk | Data portal of the measurement technology manufacturer Nivus with stations and channel values, for example from rain gauges. Access via API key. See Nivus node. |
| Nominatim | Geocoding service based on OpenStreetMap. Translates addresses into coordinates and vice versa. Usage policy: at most one request per second and a meaningful User-Agent. See Geocoder node. |
| Open Charge Map (OCM) | Open, community-maintained database of charging stations worldwide. Access via API key. |
| OpenStreetMap (OSM, OSM tag) | Free world map whose data is queried via the Overpass API and geocoded via Nominatim. Objects carry tags such as amenity or name. |
| openSenseMap (senseBox) | Open platform for environmental data from senseBox citizen sensors. See openSenseMap node. |
| OpenUV (openuv.io) | Service that provides UV index, ozone value and safe exposure times for any coordinates. Access via API key. See OpenUV node. |
| Overpass API (Overpass QL) | Query interface for OpenStreetMap data with its own query language (Overpass QL). Public servers are a fair-use offering. See Overpass node. |
| Pegelonline (WSV) | Service of the German Federal Waterways and Shipping Administration with water levels of federal waterways. See Pegelonline node. |
| The Things Network (TTN, TTI, The Things Stack) | LoRaWAN network based on The Things Stack. Its uplink messages are the default format for the Device Info node. |
| Umweltbundesamt Luftdaten (UBA) | Air data API of the German Environment Agency (UBA) with readings of the federal states and the federal government for particulate matter, nitrogen dioxide, ozone and further components. |
Formats, protocols and geodata
| Term | Meaning |
|---|---|
| Bounding box | Rectangular map section defined by minimum and maximum longitude and latitude. Used in several dialogs to select stations or objects. |
| CSV | Comma-separated values. Table format as a text file. GTFS feeds consist of CSV files; the PostgreSQL CSV endpoint delivers query results in this format. |
| GBFS | General Bikeshare Feed Specification. Standard format for shared mobility offers such as rental bikes and e-scooters, with feeds such as station_information, station_status and free_bike_status. See GBFS node. |
| GeoJSON | JSON format for geometries such as points, lines and polygons. Basis of GeoProperties in NGSI-LD. |
| GTFS (timetable) | General Transit Feed Specification. Standard format for public transport timetables as a ZIP archive of CSV files such as stops.txt, routes.txt and trips.txt. |
| GTFS Realtime (GTFS-RT) | Extension of GTFS for real-time data in Protobuf format with the feed types TripUpdates (schedule deviations), VehiclePositions (vehicle positions) and Alerts (service alerts). See GTFS Realtime node. |
| GUID | Globally unique identifier. Unique identifier of a feed entry with which the RSS Feed node detects duplicates. |
| ISO 8601 (timestamp, UTC) | International format for date and time, for example 2026-10-01T08:15:00Z. All timestamps of the nodes use this format, mostly in UTC. |
| KML / KMZ | Keyhole Markup Language, an XML format for geodata; KMZ is the compressed variant. The DWD delivers MOSMIX forecasts as KMZ. |
| LoRaWAN | Radio protocol for energy-saving sensors with long range. Devices send uplinks via gateways to a network such as The Things Network. |
| MQTT (QoS, retained message) | Lightweight messaging protocol based on the publish-subscribe principle with topics, quality of service (QoS) and retained messages. Pegelonline delivers data via MQTT. See MQTT Debug node. |
| Point-in-polygon | Geometric test whether a point lies inside a polygon. Basis of the area assignment in the Location Group node and of GTFS filtering. See Location Group node. |
| Polygon (MultiPolygon, administrative boundary) | Closed area made of coordinates, for example a municipal boundary. A MultiPolygon combines several areas. |
| PostGIS | Extension of PostgreSQL for geodata. Required for location columns in the PostgreSQL CSV endpoint. |
| PostgreSQL (SQL) | Relational database in which the platform stores, among other things, time series and export data. See PostgreSQL CSV API. |
| Protobuf (Protocol Buffers) | Compact binary data format. GTFS Realtime feeds are delivered in this format. |
| REST API | HTTP interface that exposes resources via URLs and methods such as GET and POST. Most data sources of this library are REST APIs. |
| RSS and Atom | XML formats for news feeds. Both are supported by the RSS Feed node. See RSS Feed node. |
| TLS (SSL, certificate) | Transport Layer Security. Encrypts connections to HTTPS and MQTTS services; by default the nodes verify the server certificate. |
| UUID | Universally unique identifier. 36-character identifier that identifies, for example, Pegelonline stations and Stellio subscriptions. |
| WGS 84 (coordinates, longitude, latitude) | Worldwide coordinate reference system with longitude and latitude in decimal degrees. All nodes of this library use these coordinates. |
Measurements and domain terms
| Term | Meaning |
|---|---|
| Discharge | Volume of water flowing through a river cross-section per second, given in cubic metres per second. Parameter Q at Pegelonline. |
| Alert level | Flood warning level of a gauge that is triggered when defined water levels are exceeded. |
| Soil moisture (VWC) | Volumetric water content of the soil in percent. Basis of irrigation control in green spaces. See Soil moisture node. |
| DevEUI and DeviceID | Identifiers of a LoRaWAN device: DevEUI is the globally unique hardware identifier, DeviceID the name assigned in the network. |
| Particulate matter (PM10, PM2.5) | Particles with a diameter below 10 or 2.5 micrometres, measured in micrograms per cubic metre. |
| Gateway (LoRaWAN, RX metadata) | Receiving station that forwards radio messages from LoRaWAN devices to the network. RX metadata describes which gateways received a message. |
| HQ thresholds | Flood discharges of a given return period (for example HQ10, HQ100) used as limits for alert levels. |
| Air pollutants (NO2, O3, SO2, CO) | Nitrogen dioxide, ozone, sulphur dioxide and carbon monoxide. Components of air quality measurement, in micrograms or milligrams per cubic metre. |
| MOSMIX (MOSMIX_L, station catalog) | Statistical forecasting method of the DWD. MOSMIX_L provides hourly forecasts for about ten days for several thousand stations. See DWD Weather node. |
| Water level (gauge) | Water level at a gauge, given in centimetres above the gauge datum. Parameter W at Pegelonline. |
| RSSI and SNR | Radio quality figures: RSSI is the received signal strength in dBm, SNR the signal-to-noise ratio in dB. |
| Uplink | Message that a LoRaWAN device sends to the network. Contains the decoded payload and metadata of the gateways. |
| UV index (skin type) | Measure of sunburn-effective UV radiation on an open scale starting at 0. From 3 upwards protective measures are recommended. Safe exposure times are given per skin type. |
| Look-ahead | Period in hours for which a node emits forecast values, for example in the DWD Weather or Luftdaten node. |
| Warning cell (warncell ID) | Area unit of the DWD for weather warnings, usually a municipality or district, identified by the warncell ID. See DWD Warnings node. |