ontopEO

ontopEO runs queries over Virtual Knowledge Graphs (VKG)s integrating relational data in Postgresql and openEO data from Copernicus using the [Ontop](https://ontop-vkg.org/] platform).

Description

In this repository we provide instructions and code on how to run a sample pipeline with queries over openEO using a VKG.

The entirety of the pipeline relies on 3 main components:

• Data. A database which showcases integrated Ontop queries that make use of openEO and a variety of other data into a PostgreSQL database. See the fodler db_import
• Ontop. The branch of Ontop with the openEO SPARQL functions which can be found in ontop/openeo-v2
  • A list of supported openEO functions implemented in SPARQL is present in the file OPENEO.java
  • Each function corresponds to its openEO counterpart
• PL/Python. PL/Python functions translate Ontop's SQL query with openEO arguments to an openEO process graph. They can be found in the folder pgsql

We demonstrate how the pipeline can be used to run queries over openEO data and relational data, with 8 real use cases listed in the file openeo.toml, which are adampted from examples presented in the Copernicus openEO Jupyter Notebook Samples.

Pre-requisites

Data

To run all the examples, please download:

• From MapView data for South Tyrol. In the themes to the left select "comuni" and send downloaded data to your email. Note that South Tyrol data has already been added in this repo
• Download data on administrative divisions of Campania from Geoportale Regione Campania
• Netherlands data from the Dutch National Georegister

All the files should be placed in db_import/data and a respective script to import the files should be updated in db_import/import_data.sh. For the PostGIS backend services like shp2pgsql and ogr2ogr can import the data.

openEO

Executing the example queries requires access to an openEO cloud provider. The recommended provider is Copernicus where any user needs to follow the instructions and:

• Register for an account and obtain a user ID: https://documentation.dataspace.copernicus.eu/Registration.html
• Log in and navigate to Sentinel Hub

• On the new page, navigate to "User Settings" (below on the left) and add an OAuth2 client secret

Action: Set in the file .env the two respective environment variables USER_OPENEO_CLIENT_ID and USER_OPENEO_CLIENT_SECRET based on the credentials generated in openEO

Ontop

Source code

We have also created a docker image for ontop-openeo, which we use in this example and can be updated in the docker compose file.

Mappings

For every new dataset being mapped from the PostgreSQL database to Ontop, a respective mapping needs to be added in vkg/openeo.obda. Note that unused mappings can be removed or commented using a semicolon ";". The namespace prefix we have chosen for OPENEO is http://www.openeo-ontop.org#.

Ontology

No ontology was used for this example. However, to extend the demo, please add the ontology to the vkg folder and specify in the docker compose file the property ONTOP_ONTOLOGY_FILE.

Running the demo

Please execute from the root directory of this project:

docker compose up

This will initialize a PostgreSQL database at port 7777 and Ontop at port 8081, where you can run the example queries at localhost:8081 in your browser.

Reference metadata

DOI: 10.5281/zenodo.15409222

Pano, Albulen. ontopEO: beta-1 (beta-1). Zenodo, 2025. DOI: https://doi.org/10.5281/zenodo.15423395.