stagealtmain.java

jena2.5.4推理机系统的一种最基本实现 HP实验室出品

/*
 * (c) Copyright 2007 Hewlett-Packard Development Company, LP
 * All rights reserved.
 * [See end of file]
 */

package arq.examples.bgpmatching;

import com.hp.hpl.jena.rdf.model.Model;
import com.hp.hpl.jena.rdf.model.ModelFactory;
import com.hp.hpl.jena.rdf.model.Property;
import com.hp.hpl.jena.rdf.model.Resource;
import com.hp.hpl.jena.sparql.engine.main.StageGenPropertyFunction;
import com.hp.hpl.jena.sparql.engine.main.StageGenerator;
import com.hp.hpl.jena.sparql.util.QueryExecUtils;
import com.hp.hpl.jena.sparql.util.StringUtils;

import com.hp.hpl.jena.query.ARQ;
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;

/** Example to execute a query but handle the
 *  basic graph patterns in the query in some special way.
 *  Stages are one step in executing a basic graph pattern (BGP).
 *  A StageGenerator builds a StageList and the stage list
 *  is executes with the output (a QueryIterator) of the previous
 *  stage fed int the current stage. 
 */  

public class StageAltMain
{
    static String NS = "http://example/" ;

    public static void main(String[] argv)
    {
        String[] queryString = 
        {
            "PREFIX ns: <"+NS+">" ,
            "SELECT ?v ",
            "{ ?s ns:p1 'xyz' ;",
            "     ns:p2 ?v }"
        } ;

        // The stage generator to be used for a query execution 
        // is read from the context.  There is a global context, which
        // is cloned when a query execution object (query engine) is
        // created.
        
        StageGenerator stageGenAlt = new StageGeneratorAlt() ;
        
        // Wrap in a stage generator that handles property functions -
        // stageGenAlt wil be called on sequences of triples that are
        // not property functions. 
        
        StageGenerator stageGenerator = new StageGenPropertyFunction(stageGenAlt) ;
        
        // The normal stage generator is registerd in the global context.
        // This can be replaced, so that every query execution uses the
        // alternative stage generator, or the cloned context can be
        // alter so that just one query execution is affected.

        // Change the stage generator for all queries ...
        if ( false )
            ARQ.getContext().set(ARQ.stageGenerator, stageGenerator) ;
        
        Query query = QueryFactory.create( StringUtils.join("\n", queryString)) ;
        QueryExecution engine = QueryExecutionFactory.create(query, makeData()) ;
        
        // ... or set on a per-execution basis.
        if ( true )
            engine.getContext().set(ARQ.stageGenerator, stageGenerator) ;
        
        QueryExecUtils.executeQuery(query, engine) ;
    }
    
    private static Model makeData()
    {
        Model model = ModelFactory.createDefaultModel() ;
        Resource r = model.createResource(NS+"r") ;
        Property p1 = model.createProperty(NS+"p1") ;
        Property p2 = model.createProperty(NS+"p2") ;
        model.add(r, p1, "xyz") ;
        model.add(r, p2, "abc") ;
        return model ;
    }
}

/*
 * (c) Copyright 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.
 */