Ontop

Spec sheet

Purpose

Ontop exposes relational database contents as virtual knowledge graphs and translates SPARQL queries into SQL queries executed by the source databases.Read 8 Oct 2026 · ontop-vkg.org

Product

Ontop is a Virtual Knowledge Graph system that exposes relational database content as knowledge graphs while leaving data in its source databases.Read 8 Oct 2026 · ontop-vkg.org

Deployment

Ontop can be deployed as a SPARQL endpoint using its command-line interface or Docker image.Read 8 Oct 2026 · ontop-vkg.org

License

Ontop is available under the Apache 2.0 license.Read 8 Oct 2026 · ontop-vkg.org

Headquarters

Bolzano, ItalyRead 28 Sep 2026 · ontop-vkg.org

CLI capabilities

The CLI includes commands for bootstrapping, starting an endpoint, extracting database metadata, materializing RDF, querying, validating and manipulating mappings.Read 8 Oct 2026 · ontop-vkg.org

Data handling

The graphs are virtual, so data remains in its source databases rather than being moved to another database.Read 8 Oct 2026 · ontop-vkg.org

Database driver requirement

Users must manually download the JDBC driver for their database system and place it in Ontop's jdbc directory.Read 8 Oct 2026 · ontop-vkg.org

Database integrations

Documented database systems include PostgreSQL, MySQL, MariaDB, SQL Server, Oracle, DB2, Snowflake, Databricks, Google BigQuery, AWS Redshift, DuckDB, AWS DynamoDB, and TDengine.Read 8 Oct 2026 · ontop-vkg.org

Downloads

The project says its distributions are available through GitHub, Docker Hub, SourceForge, and the Protégé plugin repository.Read 8 Oct 2026 · ontop-vkg.org

Federation integrations

Ontop supports database federators including Denodo, Dremio, Teiid, Apache Spark, Trino, PrestoDB, and AWS Athena.Read 8 Oct 2026 · ontop-vkg.org

Generic JDBC caveat

Ontop warns that generic JDBC support is not sufficient for any data source and is not guaranteed to handle every database setup and SPARQL query correctly.Read 8 Oct 2026 · ontop-vkg.org

Generic JDBC limitation

The generic JDBC implementation is not recommended because it may not handle every database setup and SPARQL query correctly; dialect-specific connectors are available for listed systems.Read 8 Oct 2026 · ontop-vkg.org

JDBC setup

Users need to download the JDBC driver for their database system and place it in Ontop’s jdbc directory.Read 8 Oct 2026 · ontop-vkg.org

Mapping editor

A plugin for the Protégé ontology editor lets users edit and test mappings, but it does not support lenses.Read 8 Oct 2026 · ontop-vkg.org

Materialization

Ontop can materialize virtual graphs into RDF files.Read 8 Oct 2026 · ontop-vkg.org

Organizations

The project says it is backed by the Free University of Bozen-Bolzano and Ontopic s.r.l., with regular contributions from Birkbeck, University of London, and Southeast University.Read 8 Oct 2026 · ontop-vkg.org

Other capabilities

Ontop supports lenses as virtual views, can materialize virtual graphs into RDF files, and provides a Protégé plugin for editing and testing mappings.Read 8 Oct 2026 · ontop-vkg.org

Plugin limitation

The Protégé plugin does not support lenses; the documentation recommends text editors or commercial offerings for advanced use.Read 8 Oct 2026 · ontop-vkg.org

Project and license

Ontop was initiated in 2009 by researchers at the Free University of Bozen-Bolzano and is available under the Apache 2.0 license.Read 8 Oct 2026 · ontop-vkg.org

Querying

Ontop translates SPARQL queries over knowledge graphs into SQL queries executed by relational data sources.Read 8 Oct 2026 · ontop-vkg.org

SPARQL support

It supports the majority of SPARQL 1.1 features, including main aggregation functions and GeoSPARQL functions.Read 8 Oct 2026 · ontop-vkg.org

Standards

It uses RDF 1.1, supports RDFS and OWL 2 QL ontologies, and supports R2RML and Ontop mappings.Read 8 Oct 2026 · ontop-vkg.org

Support and commercial offerings

The documentation says Ontopic provides a suite of solutions for leveraging Ontop and Virtual Knowledge Graphs; it does not state a support price or service level on that page.Read 8 Oct 2026 · ontop-vkg.org

Supported desktop systems

The CLI documentation provides a Windows batch file and a Unix shell script, and refers to Linux and OS X usage.Read 8 Oct 2026 · ontop-vkg.org

Where Specifiction places it

• Data Virtualization Software#11 of 257.9
• Query Engine Software#14 of 287.5
• Knowledge Graph Software#20 of 337.8