BURP-Error: A Basic and Unassuming RML Processor with RML Execution Report

BURP (Basic and Unassuming RML Processor) is a reference implementation for the new RML specification which has been written from scratch to have no influence from prior implementations of RML. BURP was created to serve as a reference RML implementation for the Knowledge Graph Construction community and to verify the RML specifications, their feasibility, and coverage of their test cases.

BURP-Error is a fork of BURP that adds error handling to the RML processor, according to the RML Execution Report. The project is a proof of concept, no maintenance guaranteed, but if you have any questions or issues, feel free to open an issue on GitHub.

Warning: Joins are quadratic, in terms of iterations and number of multivalued join conditions values.

Coverage matrix

RML module	Test Cases: Pass / Fail / Total
RML-Core	✔️ 76 / 0 / 76
RML-IO	🚧 54 / 19 / 73
RML-IO-Registry	✔️ 52 / 50 / 102 Details below
RML-CC	✅ 35 / 0 / 35
RML-FNML	✅️ 19 / 1 / 20
RML-Star	❌ Not implemented
RML-LV	✅️ 41 / 0 / 41
RER	🪅 Demo implementation

RML-IO-Registry coverage details

BURP supports natively the following input sources:

• rml:FilePath or rml:RelativePathSource — local files (supports rml:root and rml:path)

• rml:CSV — CSV files (including CSVW tables and their dialects: encoding, delimiter, header, nulls)

• rml:JSONPath — JSON sources (RFC 9535 JSONPath iterator)

• rml:XPath — XML sources (XPath 1.0 iterator; supports namespace/prefix mappings for XPath reference formulations)

• rml:SPARQL Results (CSV/TSV/XML/JSON) — SPARQL result files, SPARQL endpoints/services and data dumps (VOID/SD)

• rml:SQL2008Query and rml:SQL2008Table — relational database sources (via D2RQ properties such as d2rq:jdbcDSN, d2rq:jdbcDriver, username, password)

• DCAT Distribution / CSVW Table — remote files via DCAT downloadURL or CSVW url

• Extensions possible see extending BURP

Using BURP

The run the R2RML processor, execute the following command:

$ java -jar burp.jar [-h] [-b=<baseIRI>] -m=<mappingFile> [-o=<outputFile>]

A fat jar is provided with the Gradle Shadow plugin.

Usage: burp [-h] [-b=<baseIRI>] -m=<mappingFile> [-o=<outputFile>]
  -b, --baseIRI=<baseIRI>   Used in resolving relative IRIs produced by the RML mapping
  -h, --help                Display a help message
  -m, --mappingFile=<mappingFile>
                            The RML mapping file
  -o, --outputFile=<outputFile>
                            The output file

If no outputFile is provided and the RML mapping does not rely on RML-IO for targets, then the output is written to the standard output.

Extending BURP

BURP can be extended by providing additional logical source providers (for new input sources) and custom RML-FNML functions. BURP discovers extensions on the classpath using Java's ServiceLoader mechanism.

For complete documentation, see ExtensionPoints.md

What you can extend:

• Logical source providers (burp.ls.LogicalSourceProvider) — add support for new reference formulations or custom source types
• RML functions (burp.model.fnmlutil.RMLFunction) — provide custom function behavior for FNML mappings

Quick example:

# Run BURP with your extension JAR on the classpath
java -cp "burp.jar:your-extension.jar" burp.Main -m mapping.ttl -o output.ttl

Building BURP

To build the project, you will need Java, Kotlin and Gradle (via ./gradlew).

./gradlew build

To package the fat JAR (Shadow JAR):

./gradlew clean shadowJar

The tests rely on Docker for mappings on MySQL, PostgreSQL, and MSSQL.

To update resources from specifications:

./gradlew fetchTestCases
./gradlew fetchVocabularyAndShapes

Release

1. Set the version in build.gradle.kts, then commit

git add build.gradle.kts README.md
git commit -m "release: v0.1.4"

2. Create an annotated tag with a description (they can be reused as GitHub release notes)

git tag -a v0.1.4 -m "v0.1.4\n\n- short release notes here"

3. Push commit and tag

git push
git push origin v0.1.4

4. Build release artefact

./gradlew clean shadowJar

5. Create the GitHub release with the shadow jar and reusable the release notes

gh release create v0.1.4 build/libs/burp.jar --notes-from-tag

Citation

If you use BURP-Error, please cite our paper:

@inproceedings{duchateau2026rml-execution-report,
  author       = {Jakub Duchateau and Dylan {Van Assche} and Christophe Debruyne},
  editor       = {},
  title        = {Beyond Exit Code 1: A Vocabulary for Execution Report of RML Processors (RER)},
  booktitle    = {Proceedings of the 7th International Workshop on Knowledge Graph Construction
                  co-located with 23rd Extended Semantic Web Conference ({ESWC} 2026),
                  Dubrovnik, Croatia, May 10, 2026},
  series       = {{CEUR} Workshop Proceedings},
  volume       = {X},
  publisher    = {CEUR-WS.org},
  year         = {2026},
  url          = {https://ceur-ws.org/Vol-X/paperX.pdf}
}

If you use BURP, please cite our paper:

@inproceedings{DBLP:conf/kgcw/AsscheD24,
  author       = {Dylan {Van Assche} and Christophe Debruyne},
  editor       = {David Chaves{-}Fraga and Anastasia Dimou and
                  Ana Iglesias{-}Molina and Umutcan Serles and
                  Dylan {Van Assche}},
  title        = {BURPing Through {RML} Test Cases},
  booktitle    = {Proceedings of the 5th International Workshop on Knowledge Graph Construction
                  co-located with 21th Extended Semantic Web Conference ({ESWC} 2024),
                  Hersonissos, Greece, May 27, 2024},
  series       = {{CEUR} Workshop Proceedings},
  volume       = {3718},
  publisher    = {CEUR-WS.org},
  year         = {2024},
  url          = {https://ceur-ws.org/Vol-3718/paper4.pdf}
}

License

BURP is released under the MIT license.