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/**
 *
 * Copyright (C) 2011, NUI Galway.
 * All rights reserved.
 *
 * The software in this package is published under the terms of the BSD style license a copy of which has been included
 * with this distribution in the bsb_license.txt file and/or available on NUI Galway Server at
 * http://xsparql.deri.ie/license/bsd_license.txt
 *
 * Created: 09 February 2011, Reasoning and Querying Unit (URQ), Digital Enterprise Research Institute (DERI) on behalf of
 * NUI Galway.
 */
/**
 * 
 */
package org.deri.sparql;

import org.deri.xsparql.rewriter.Helper;
import org.w3c.dom.Document;

import com.hp.hpl.jena.query.Dataset;
import com.hp.hpl.jena.query.Query;
import com.hp.hpl.jena.query.QueryExecution;
import com.hp.hpl.jena.query.QueryExecutionFactory;
import com.hp.hpl.jena.query.QueryFactory;
import com.hp.hpl.jena.query.ResultSet;
import com.hp.hpl.jena.query.ResultSetFormatter;

/**
 * Use the ARQ API to pose SPARQL queries
 * 
 * @author Nuno Lopes
 * 
 */
public class SPARQLQuery {

  private String query;
  private Dataset dataset = null;

  // ----------------------------------------------------------------------------------------------------
  // SPARQL

  /**
   * Creates a new SPARQLQuery instance.
   * 
   */
  public SPARQLQuery(String query) {
    this.query = query;
    this.dataset = null;
  }

  /**
   * Creates a new SPARQLQuery instance.
   * 
   */
  public SPARQLQuery(String query, Dataset dataset) {
    this.query = query;
    this.dataset = dataset;
  }

  /**
   * Evaluates a SPARQL query.
   * 
   * @return XML ResultSet with the results of the query
   */
  public ResultSet getResults() {

    Query q = QueryFactory.create(query);
    QueryExecution qe;

    if (dataset == null) {
      qe = QueryExecutionFactory.create(q);
    } else {
      qe = QueryExecutionFactory.create(query, dataset);
    }

    return qe.execSelect();
  }

  /**
   * Evaluates a SPARQL query and return the XML format.
   * 
   * @return XML results of the query
   */
  public Document getResultsAsXML() {
    ResultSet resultSet = getResults();

    String xml = ResultSetFormatter.asXMLString(resultSet);

    return Helper.parseXMLString(xml);
  }

}