isliteral.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.sail.query;

import java.util.Collection;

import org.openrdf.model.Literal;

import org.openrdf.sesame.sail.RdfSource;

public class IsLiteral implements BooleanExpr {

/*-------------------------------------------+
| Variables                                  |
+-------------------------------------------*/

	protected Var _var;

/*-------------------------------------------+
| Constructors                               |
+-------------------------------------------*/

	public IsLiteral(Var var) {
		_var = var;
	}

/*-------------------------------------------+
| Methods                                    |
+-------------------------------------------*/

	/**
	 * Determines whether the operand (a variable) contains a Literal.
	 *
	 * @return <code>true</code> if the operand contains a Literal,
	 * <code>false</code> otherwise.
	 **/
	public boolean isTrue(RdfSource rdfSource)
		throws SailQueryException
	{
		return _var.getValue() instanceof Literal;
	}

	public void getVariables(Collection variables) {
		_var.getVariables(variables);
	}

	public String toString() {
		return "isLiteral(" + _var + ")";
	}
}