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Jena is a Java framework for building Semantic Web applications. It provides a programmatic environment for RDF, RDFS and OWL, SPARQL and includes a rule-based inference engine.
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/******************************************************************
 * File:        TripleMatchFrame.java
 * Created by:  Dave Reynolds
 * Created on:  23-Jul-2003
 * 
 * (c) Copyright 2003, 2004, 2005, 2006, 2007, 2008, 2009 Hewlett-Packard Development Company, LP
 * [See end of file]
 * $Id: TripleMatchFrame.java,v 1.10 2009/01/29 09:37:02 chris-dollin Exp $
 *****************************************************************/
package com.hp.hpl.jena.reasoner.rulesys.impl;

import com.hp.hpl.jena.graph.*;
import com.hp.hpl.jena.util.iterator.ExtendedIterator;

/**
 * Frame on the choice point stack used to represent the state of a direct
 * graph triple match.
 * 
 * This is used in the inner loop of the interpreter and so is a pure data structure
 * not an abstract data type and assumes privileged access to the interpreter state.
 * 
 *  
 * @author Dave Reynolds
 * @version $Revision: 1.10 $ on $Date: 2009/01/29 09:37:02 $
 */
public class TripleMatchFrame extends GenericTripleMatchFrame {
    
    /** An iterator over triples matching a goal */
    ExtendedIterator matchIterator;
    
    /**
     * Constructor.
     * Initialize the triple match to preserve the current context of the given
     * LPInterpreter and search for the match defined by the current argument registers
     * @param intepreter the interpreter instance whose env, trail and arg values are to be preserved
     */
    public TripleMatchFrame(LPInterpreter interpreter) {
        init(interpreter);
    }

    /**
     * Find the next result triple and bind the result vars appropriately.
     * @param interpreter the calling interpreter whose trail should be used
     * @return false if there are no more matches in the iterator.
     */
    public boolean nextMatch(LPInterpreter interpreter) {
        while (matchIterator.hasNext()) {
            if (bindResult(matchIterator.next(), interpreter)) {
                return true;
            }
        }
        return false;
    }
    
    /**
     * Initialize the triple match to preserve the current context of the given
     * LPInterpreter and search for the match defined by the current argument registers
     * @param intepreter the interpreter instance whose env, trail and arg values are to be preserved
     */
    @Override public void init(LPInterpreter interpreter) {
        super.init(interpreter);
        this.matchIterator = interpreter.getEngine().getInfGraph().findDataMatches(goal);
    }
    
    /**
     * Override close method to reclaim the iterator.
     */
    @Override public void close() {
        if (matchIterator != null) matchIterator.close();
    }
    
}


/*
    (c) Copyright 2003, 2004, 2005, 2006, 2007, 2008, 2009 Hewlett-Packard Development Company, LP
    All rights reserved.

    Redistribution and use in source and binary forms, with or without
    modification, are permitted provided that the following conditions
    are met:

    1. Redistributions of source code must retain the above copyright
       notice, this list of conditions and the following disclaimer.

    2. Redistributions in binary form must reproduce the above copyright
       notice, this list of conditions and the following disclaimer in the
       documentation and/or other materials provided with the distribution.

    3. The name of the author may not be used to endorse or promote products
       derived from this software without specific prior written permission.

    THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
    IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
    OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
    IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
    INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
    NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
    DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
    THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
    (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
    THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/