Query to GraphDB's repository with custom functions SPARQL using Jena

I've implemented some custom functions SPARQL with Jena ARQ following the Property Function docs. Those functions work with a local dataset using a model:

Model model = ModelFactory.createDefaultModel();

model.read(new FileInputStream("data/data.ttl"), null, "TTL");

Query query = QueryFactory.create(queryString) ; // the queryString contains a custom property function defined with Jena

try (QueryExecution qexec = QueryExecutionFactory.create(query, model)) {
		   ...
		  }

However, I need to apply these property functions for queries on a dataset on my Graphdb Repository, so I tried to connect program to GraphDB using Jena.

I've tried following Using GraphDB with Jena but it seems out of date and cannot be implemented because SailRepository.initialize(); was deprecated and SesameDataset doesn't longer exist to initialize my model.

import org.eclipse.rdf4j.repository.sail.SailRepository;
import org.eclipse.rdf4j.repository.RepositoryConnection;
import com.ontotext.jena.SesameDataset;

...
RepositoryConnection connection = repository.getConnection();

// finally, create the DatasetGraph instance
SesameDataset dataset = new SesameDataset(connection);

I've also tried RDFConnection of Jena but it doesn't work with my custom functions since there's no model backend to apply queries.

Can anyone tell me where can I find the SesameDataset to import or whether there is other way to query a GraphDB's repository with custom functions?

You would probably make your life a lot easier by using RDF4J to communicate with GraphDB, instead of Jena - it is the recommended Java API for this purpose by the GraphDB developers.

You can implement custom SPARQL functions in RDF4J/GraphDB by following this tutorial - in summary it's a matter of implementing the org.eclipse.rdf4j.query.algebra.evaluation.function.Function interface and making sure your implementation is on the classpath of GraphDB and registered as an SPI implementation.

Jeen (the creator of rdf4j) pointed how you can create custom functions.

However, as AndyS (the creator of Jena) points out, you seem to need magic predicates (custom property functions). For that I think that you need to create a plugin and implement pattern interpretation as described here: http://graphdb.ontotext.com/documentation/standard/plug-in-api.html#pattern-interpretation.

Most plugins are open source at https://github.com/Ontotext-AD, so you can see many examples. I know for sure that https://github.com/Ontotext-AD/graphdb-geosparql-plugin uses magic predicates, eg

• ?x geo:sfWithin ?y is a predicate that checks (or returns) all features where ?x is within ?y
• geof:sfWithin(?x,?y) (note the different namespace) is a function that checks the same condition, but must be called with bound params: it cannot find features satisfying the condition.

See this search and then see IRI GEO_SF_WITHIN, search with GEO_SF_WITHIN, and you find com/ontotext/trree/geosparql/GeoSparqlFunction.java and com/useekm/geosparql/algebra/PropertyToFunctionOptimizer.java