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r2rml-kit – Export relational databases to RDF with R2RML

r2rml-kit is an implementation of W3C's R2RML and Direct Mapping standards. It can:

  • Generate an R2RML mapping by inspecting a relational database schema
  • Validate R2RML mapping files
  • Dump the contents of a database to an RDF file according to an R2RML mapping
  • Dump the contents of a database to an RDF file according to the W3C Direct Mapping
  • Access the contents of a database through the Jena API

Besides R2RML, r2rml-kit also supports the D2RQ mapping language.

r2rml-kit is an offshoot of D2RQ, based on its abandoned develop branch. Unlike D2RQ, it does not support SPARQL, and does not include a server application equivalent to D2RQ's D2R Server.

r2rml-kit is currently in pre-alpha stage. It is not yet fully separated from the D2RQ codebase, and many things will not yet work. It does not support R2RML's named graph features. See TODO.md for a short-term roadmap.

Running r2rml-kit

After building with mvn compile, you can test-run the various components. Let's assume you have a MySQL database called mydb on your machine.

Generating a default mapping file

./generate-mapping -u root -o mydb.ttl jdbc:mysql:///mydb

This generates a mapping file mydb.ttl for your database.

Validating an R2RML mapping

./validate mydb.ttl

This validates the mapping file mydb.ttl.

Dumping the database

./dump-rdf -m mydb.ttl -o dump.nt

This creates dump.nt, a dump containing the mapped RDF in N-Triples format.

Running the unit tests

The unit tests can be executed with mvn test.

Some unit tests rely on MySQL being present, and require that two databases are created:

  1. A database called iswc that contains the data from src/test/resources/example/iswc-mysql.sql:

    echo "CREATE DATABASE iswc" | mysql -u root mysql -u root iswc < src/test/resources/example/iswc-mysql.sql

  2. An empty database called D2RQ_TEST.