instanceof.java

这是外国一个开源推理机

/*  Sesame - Storage and Querying architecture for RDF and RDF Schema
 *  Copyright (C) 2001-2005 Aduna
 *
 *  Contact: 
 *  	Aduna
 *  	Prinses Julianaplein 14 b
 *  	3817 CS Amersfoort
 *  	The Netherlands
 *  	tel. [phone]
 *  	fax. [phone]
 *
 *  	http://aduna.biz/
 *  	http://www.openrdf.org/
 *  
 *  This library is free software; you can redistribute it and/or
 *  modify it under the terms of the GNU Lesser General Public
 *  License as published by the Free Software Foundation; either
 *  version 2.1 of the License, or (at your option) any later version.
 *
 *  This library is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 *  Lesser General Public License for more details.
 *
 *  You should have received a copy of the GNU Lesser General Public
 *  License along with this library; if not, write to the Free Software
 *  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */

package org.openrdf.sesame.query.rql.model;

import java.io.IOException;

import org.openrdf.model.Resource;
import org.openrdf.model.impl.URIImpl;

import org.openrdf.sesame.query.QueryEvaluationException;
import org.openrdf.sesame.query.TableQueryResultListener;
import org.openrdf.sesame.query.rql.model.iterators.NestedValueIterator;
import org.openrdf.sesame.query.rql.model.iterators.StatementSubjectIterator;
import org.openrdf.sesame.sail.RdfSchemaSource;
import org.openrdf.sesame.sail.ResourceIterator;
import org.openrdf.sesame.sail.StatementIterator;
import org.openrdf.sesame.sail.ValueIterator;
import org.openrdf.sesame.sail.util.EmptyValueIterator;

public class InstanceOf implements DataQuery {

	protected ClassQuery _classQ;

	protected boolean _properInstances;

	public InstanceOf(ClassQuery classQ, boolean properInstances) {
		_classQ = classQ;
		_properInstances = properInstances;
	}

	public void evaluate(RdfSchemaSource rss, TableQueryResultListener listener)
		throws QueryEvaluationException
	{
		ValueIterator iter = null;

		try {
			listener.startTableQueryResult();

			iter = getInstances(rss);
			while (iter.hasNext()) {
				listener.startTuple();
				listener.tupleValue(iter.next());
				listener.endTuple();
			}

			listener.endTableQueryResult();
		}
		catch (IOException e) {
			throw new QueryEvaluationException(e);
		}
		finally {
			if (iter != null) {
				iter.close();
			}
		}
	}

	public ValueIterator getResources(RdfSchemaSource rss)
		throws QueryEvaluationException
	{
		return getInstances(rss);
	}

	public ValueIterator getInstances(RdfSchemaSource rss)
		throws QueryEvaluationException
	{
		ResourceIterator classIter = _classQ.getClasses(rss);
		return new Iterator(rss, classIter);
	}

	public boolean returnsSet() {
		return true;
	}

	public String getQuery() {
		return this.toString();
	}

	public String toString() {
		if (_properInstances) {
			return "^" + _classQ.toString();
		}
		else {
			return _classQ.toString();
		}
	}

	/*---------------------------------------------------+
	 | Iterator                                           |
	 +---------------------------------------------------*/

	class Iterator extends NestedValueIterator {

		protected RdfSchemaSource _rss;

		public Iterator(RdfSchemaSource rss, ResourceIterator classIter) {
			super(classIter);
			_rss = rss;
		}

		public ValueIterator getInnerIterator(Resource classRes) {
			if (classRes.equals(URIImpl.RDFS_LITERAL)) {
				//return _rss.getLiteral(null, null, null);
				return new EmptyValueIterator();
			}
			else {
				StatementIterator statIter;
				if (_properInstances) {
					statIter = _rss.getDirectType(null, classRes);
				}
				else {
					statIter = _rss.getType(null, classRes);
				}
				return new StatementSubjectIterator(statIter);
			}
		}
	}
}