RAW ⨯ Jena

Apache Jena is a free and open source Java framework for building Semantic Web and Linked Data applications. It allows users to execute SPARQL queries from start to finish (granted they finish before a preset timeout). Unfortunately, it lacks of a very useful feature: sampling [1].

RAW ⨯ Jena [2] fills this gap by performing RAndom Walks over queries, and by processing cardinality estimates [3]. This enables getting random elements, processing aggregations, optimizing join order, building summaries etc.



Dependencies and configurations

• Java 21
• ~/.m2/settings.xml configured to include https://maven.pkg.github.com/Chat-Wane/sage-jena. See an example in settings.xml. You need to generate credentials. This requirement is meant to disappear in the future as either we publish on Maven's central repository, or GitHub allows downloading without credentials.
  • Alternatively, clone and install the old way.

Usage

# Get command help
mvn exec:java -pl raw-jena-module -Dexec.args="--help"

# Usage: <main class> [-h] [--database=<database>] [--limit=<limit>]
#                     [--port=<port>] [--timeout=<timeout>] [--ui=<ui>]
#                     [-v=<verbosity>]
#       --database=<database>   The path to your TDB2 database (default: downloads Watdiv10M).
#       --limit=<limit>         The maximum number of random walks per query (default: 10K).
#       --port=<port>           The port that gives access to the database (default: 3330).
#       --timeout=<timeout>     The maximal duration of random walks (default: 60K ms).
#       --ui=<ui>               The path to your UI folder (default: None).
#   -h, --help                  Display this help message.
#   -v, --verbosity=<verbosity> The verbosity level (ALL, INFO, FINE) (default: None).

# Run a server allowing random walks on your Apache Jena TDB2 database.
# Alternatively, without arguments, it will download and serve WatDiv10M.
mvn exec:java -pl raw-jena-module -Dexec.args="--database=/path/to/jena/tdb2/database"

# Install the dependencies of the website
npm install --prefix ./raw-jena-ui

# Serve the Web graphical user interface
vite ./raw-jena-ui



References

[1] S. Agarwal, H. Milner, A. Kleiner, A. Talwalkar, M. I. Jordan, S. Madden, B. Mozafari, I. Stoica, Knowing when you’re wrong: Building fast and reliable approximate query processing systems.

[2] J. Aimonier-Davat, M.-H. Dang, P. Molli, B. Nédelec, and H. Skaf-Molli, RAW-JENA: Approximate Query Processing for SPARQL Endpoints.

[3] F. Li, B. Wu, K. Yi, Z. Zhao, Wander Join and XDB: Online Aggregation via Random Walks.