topleveltriplematchframe.java

jena2.5.4推理机系统的一种最基本实现 HP实验室出品

/******************************************************************
 * File:        TopLeveTripleMatchFrame.java
 * Created by:  Dave Reynolds
 * Created on:  11-Aug-2003
 * 
 * (c) Copyright 2003, 2004, 2005, 2006, 2007 Hewlett-Packard Development Company, LP
 * [See end of file]
 * $Id: TopLevelTripleMatchFrame.java,v 1.6 2007/01/02 11:48:41 andy_seaborne Exp $
 *****************************************************************/
package com.hp.hpl.jena.reasoner.rulesys.impl;

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

/**
 * 
 * @author <a href="mailto:[e-mail]">Dave Reynolds</a>
 * @version $Revision: 1.6 $ on $Date: 2007/01/02 11:48:41 $
 */
public class TopLevelTripleMatchFrame extends GenericChoiceFrame {

    /** The last returned triple */
    protected Triple lastMatch;
    
    /** An iterator over triples matching a goal */
    ExtendedIterator matchIterator;

    /** Used for debug/tracing only */
    protected TriplePattern goal;
        
    /**
     * 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 TopLevelTripleMatchFrame(LPInterpreter interpreter, TriplePattern goal) {
        init(interpreter);
        this.matchIterator = interpreter.getEngine().getInfGraph().findDataMatches(goal);
        this.goal = goal;
    }

    /**
     * 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) {
        if (matchIterator.hasNext()) {
            lastMatch = (Triple)matchIterator.next();
            return true;
        } else {
            return false;
        }
    }
        
    /**
     * Override close method to reclaim the iterator.
     */
    public void close() {
        if (matchIterator != null) matchIterator.close();
    }
        
}


/*
    (c) Copyright 2003, 2004, 2005, 2006, 2007 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.
*/