AGSparqlDescribe.java

package com.franz.ag.examples;

import com.franz.ag.*;

public class AGSparqlDescribe {

    /**
     * Demonstrates some basics of using DESCRIBE in SPARQL
     * 
     * @param args unused
     * @throws AllegroGraphException 
     */
    public static void main(String[] args) throws AllegroGraphException {
        
        // Connect to server, which must already be running.
        AllegroGraphConnection ags = new AllegroGraphConnection();
        try {
            ags.enable();
        } catch (Exception e) {
            throw new AllegroGraphException("Server connection problem", e);
        }
        
        // Create fresh triple-store for this example.
        AllegroGraph ts = ags.renew("sparql", AGPaths.TRIPLE_STORES);
                
        // Register any namespaces
        ts.registerNamespace("foaf", "http://xmlns.com/foaf/0.1/");

        // Define blank nodes
        BlankNode a = (BlankNode)ts.createBNode("_:a");
        BlankNode b = (BlankNode)ts.createBNode("_:b");
        
        // Add some data to the store
        ts.addStatement(a,"!rdf:type","!foaf:Person");
        ts.addStatement(a,"!foaf:name",ts.createLiteral("Alice"));
        ts.addStatement(a,"!foaf:mbox","<mailto:alice@example.com>");
        ts.addStatement(a,"!foaf:mbox","<mailto:alice@work.example>");
        ts.addStatement(b,"!rdf:type","!foaf:Person");
        ts.addStatement(b,"!foaf:name",ts.createLiteral("Bob"));
        ts.addStatement(b,"!foaf:homepage","<http://work.example.org/alice/>");

        // This query requests that an RDF graph be returned containing
        // data describing resources that have the specified foaf:mbox.
        String query = 
        "PREFIX foaf:   <http://xmlns.com/foaf/0.1/> " +
        "DESCRIBE ?x " +
        "WHERE    { ?x foaf:mbox <mailto:alice@example.com> } ";
        
        // Query the store and show the resulting graph
        SPARQLQuery sq = new SPARQLQuery();
        Cursor cc = sq.describe(ts,query);
        AGUtils.showTriples(cc,ts);
        
        // Close the triple store and disconnect from the server.
        ts.closeTripleStore();
        ags.disable();
    }

}

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