qgisparql-layer2triple

Layer2Triple

A QGIS plugin to export geographic vector layers as RDF triples in Turtle (.ttl) format, enabling integration with linked data ecosystems.

Part of the QGISParQL suite — see also Triple2Layer.

Overview

Layer2Triple converts QGIS vector layers (points, lines, polygons) into RDF (Resource Description Framework) data using the GeoSPARQL standard. Users can map layer attributes to ontology concepts, define namespaces and prefixes, and export the results as Turtle (.ttl) or XML files ready for ingestion into triple stores or linked data portals.

The plugin bridges GIS and Semantic Web workflows, enabling geospatial data to be published as linked open data.

Features

Export QGIS vector layers to RDF Turtle (.ttl) or XML format
Load custom OWL vocabularies from remote URLs to map layer attributes
Map attributes to ontology properties (Constant Value, Layer Attribute, or Vocabulary)
Define base URL, RDF type, and namespace prefix for generated resources
Save and reload export configurations as JSON files
Filter and select specific features or all features in the layer
Generate unique resource identifiers (UUID) or use an existing layer attribute as ID
Group observations into a named dataset (qb:DataSet) via constant aggregations

Requirements

QGIS 3.0 or higher
Python 3.x (tested on Python 3.10–3.12)
Python packages: rdflib

Installation

From QGIS Plugin Repository (recommended)

Open QGIS and go to Plugins → Manage and Install Plugins
Search for Layer2Triple
Click Install

Manual installation

Download or clone this repository
Copy the folder to your QGIS plugins directory:
- Linux: ~/.local/share/QGIS/QGIS3/profiles/default/python/plugins/
- Windows: %APPDATA%\QGIS\QGIS3\profiles\default\python\plugins\
Restart QGIS and enable the plugin under Plugins → Manage and Install Plugins

Installing Python Dependencies

QGIS does not install external Python packages automatically. You must install them manually in your QGIS Python environment to avoid ModuleNotFoundError.

On Windows

Open the OSGeo4W Shell as Administrator and run:

pip install rdflib

On Linux / macOS

Open your terminal and run:

pip install rdflib --break-system-packages

requirements.txt

rdflib

Usage

Open a QGIS project containing at least one vector layer
Go to Vector → QGISParQL → Layer2Triple
Select the layer to export in the Layer dropdown
(Optional) Load an OWL vocabulary via Vocabulary → Load Vocabulary
Click Load Layer to populate the attribute table
Map each attribute by selecting a concept and its type (Constant Value, Layer Attribute, or Vocabulary)
Set the Base URL, Prefix, and RDF Type for the output resources
(Optional) Save the configuration via Settings → Save for reuse
Click Save and choose the output file path

For a full walkthrough with screenshots, see the documentation.

Example output (Turtle format)

@prefix obs: <https://purl.org/dbcells/observation#> .
@prefix geo: <http://www.opengis.net/ont/geosparql#> .
@prefix dbc: <https://purl.org/linked-data/dbcells#> .

obs:a1b2c3d4 a qb:Observation ;
    dbc:resolution 8.3e-02 ;
    geo:asWKT "Polygon ((-34.83 -6.92, ...))" .

Triple2Layer — the companion plugin that imports SPARQL query results from triple stores back into QGIS as vector layers.

Authors

Sérgio Souza Costa — @profsergiocosta — sergio.costa@ufma.br
Nerval Junior — @nervaljunior

Universidade Federal do Maranhão (UFMA) — LambdaGeo Research Group

Citation

If you use this plugin in your research, please cite:

@software{costa2024layer2triple,
  author  = {Costa, Sérgio Souza and Junior, Nerval},
  title   = {Layer2Triple: A QGIS Plugin for Exporting Geographic Data as RDF Triples},
  year    = {2024},
  url     = {https://github.com/LambdaGeo/qgisparql-layer2triple}
}

License

This project is licensed under the GNU General Public License v2.0 — see the LICENSE file for details.

Contributing

Contributions are welcome! Please open an issue or submit a pull request.

This site is open source. Improve this page.