SPARQL

Query application tables with RDF vocabulary through the common GraphEngine.

Choose the data model

For a property graph, define an OntologyMapping that maps class and predicate IRIs to graph labels and properties. Use it with GraphEngine::sparql. The older MappedGraphEngine::sparql method remains available on the compatibility facade.

For explicit column, identity, and named-graph mappings, add RdfMapping rules to GraphMapping and call GraphEngine::sparql_query. The RDF guide covers ordinary tables, composite foreign keys, and updates. On mapped engines, existing ontology builders translate to these same rules; patterns do not require an explicit type root.

Define a vocabulary

This vocabulary describes the people and social relationships in the mapped tutorial:

use orchiddb::ir::plan::Direction;
use orchiddb::language::sparql::OntologyMapping;

let ontology = OntologyMapping::new()
    .class("https://example.com/Person", "Person")
    .property("https://example.com/name", "Person", "name")
    .property("https://example.com/age", "Person", "age")
    .relationship_between(
        "https://example.com/follows", "FOLLOWS", Direction::Out,
        "Person", "Person",
    );

The ontology guide explains identity properties and the builder methods.

Select properties

PREFIX ex: <https://example.com/>
SELECT ?name ?age WHERE {
  ?person a ex:Person ; ex:name ?name ; ex:age ?age .
  FILTER(?age >= 30)
}
ORDER BY ?name

The prefix abbreviates IRIs. a expresses an RDF type. Variables begin with ?, and FILTER applies a condition to the matched bindings.

Run the query through a mapped engine:

let result = graph.sparql(
    "PREFIX ex: <https://example.com/> \
     SELECT ?name WHERE { ?p a ex:Person ; ex:name ?name . } ORDER BY ?name",
    ontology.clone(),
).await?;

result.returned.batch contains Arrow data, and result.returned.fields contains output binding names. The ontology convenience method returns legacy scalar columns. For typed RDF terms, use sparql_query(query, dataset); for Arrow RDF term metadata and execution statistics, use sparql_dataset(query, dataset).

Join relationships

PREFIX ex: <https://example.com/>
SELECT ?name WHERE {
  ?person a ex:Person ; ex:name "alice" ; ex:follows ?friend .
  ?friend ex:name ?name .
}
ORDER BY ?name

Shared variables connect patterns. The ontology resolves ex:follows to the mapped FOLLOWS relationship.

Shape a result

Use SELECT DISTINCT to remove repeated projected bindings. Use ORDER BY for result ordering and LIMIT with OFFSET for a result window.

PREFIX ex: <https://example.com/>
SELECT DISTINCT ?name WHERE {
  ?person a ex:Person ; ex:name ?name .
}
ORDER BY ?name
LIMIT 20
OFFSET 0

Query named graphs

RDF datasets can include a graph column. Use GRAPH to choose a named graph and FROM or FROM NAMED to define the active dataset for a query. See RDF datasets for the source mapping and examples.

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