CONSTRUCT Queries

CONSTRUCT queries generate RDF graphs from query results, enabling you to transform and reshape data into new graph structures.

Overview

CONSTRUCT queries return RDF graphs instead of variable bindings. They're useful for:

Extracting subgraphs
Transforming data structures
Creating new graph views
Generating RDF for export

Basic CONSTRUCT

SPARQL CONSTRUCT

PREFIX ex: <http://example.org/ns/>

CONSTRUCT {
  ?person ex:displayName ?name .
}
WHERE {
  ?person ex:name ?name .
}

This generates a new graph with ex:displayName properties from ex:name values.

Multiple Triples

Construct multiple triples per solution:

PREFIX ex: <http://example.org/ns/>

CONSTRUCT {
  ?person ex:displayName ?name .
  ?person ex:hasAge ?age .
}
WHERE {
  ?person ex:name ?name .
  ?person ex:age ?age .
}

Complex Patterns

Conditional Construction

Use filters to conditionally construct triples:

PREFIX ex: <http://example.org/ns/>

CONSTRUCT {
  ?person ex:status ex:Adult .
}
WHERE {
  ?person ex:age ?age .
  FILTER (?age >= 18)
}

Transitive Relationships

Construct inferred relationships:

PREFIX ex: <http://example.org/ns/>

CONSTRUCT {
  ?person ex:knows ?friendOfFriend .
}
WHERE {
  ?person ex:friend ?friend .
  ?friend ex:friend ?friendOfFriend .
}

CONSTRUCT with Aggregation

Construct triples from aggregated data:

PREFIX ex: <http://example.org/ns/>

CONSTRUCT {
  ?category ex:productCount ?count .
}
WHERE {
  {
    SELECT ?category (COUNT(?product) AS ?count)
    WHERE {
      ?product ex:category ?category .
    }
    GROUP BY ?category
  }
}

Use Cases

Extract Subgraph

Extract a subgraph for a specific entity:

PREFIX ex: <http://example.org/ns/>

CONSTRUCT {
  ?s ?p ?o .
}
WHERE {
  ex:alice ?p ?o .
  BIND (ex:alice AS ?s)
}

Transform Data Structure

Transform data into a different structure:

PREFIX ex: <http://example.org/ns/>

CONSTRUCT {
  ?order ex:hasItem [
    ex:product ?product ;
    ex:quantity ?quantity
  ] .
}
WHERE {
  ?order ex:item ?item .
  ?item ex:product ?product .
  ?item ex:quantity ?quantity .
}

Generate Inferred Facts

Generate inferred relationships:

PREFIX ex: <http://example.org/ns/>

CONSTRUCT {
  ?person ex:ancestor ?ancestor .
}
WHERE {
  ?person ex:parent+ ?ancestor .
}

Best Practices

Specific Patterns: Construct specific patterns rather than wildcards
Filter Early: Apply filters in WHERE clause, not CONSTRUCT
Avoid Duplicates: Use DISTINCT if needed
Performance: CONSTRUCT can be expensive for large result sets