Package arq.examples

Source Code of arq.examples.AlgebraExec

/*
* (c) Copyright 2007, 2008, 2009 Hewlett-Packard Development Company, LP
* All rights reserved.
* [See end of file]
*/

package arq.examples;

import java.util.ArrayList ;
import java.util.List ;

import com.hp.hpl.jena.datatypes.xsd.XSDDatatype ;
import com.hp.hpl.jena.graph.Node ;
import com.hp.hpl.jena.graph.Triple ;
import com.hp.hpl.jena.query.ResultSet ;
import com.hp.hpl.jena.query.ResultSetFormatter ;
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.RDFNode ;
import com.hp.hpl.jena.rdf.model.Resource ;
import com.hp.hpl.jena.sparql.algebra.Algebra ;
import com.hp.hpl.jena.sparql.algebra.Op ;
import com.hp.hpl.jena.sparql.algebra.op.OpBGP ;
import com.hp.hpl.jena.sparql.algebra.op.OpFilter ;
import com.hp.hpl.jena.sparql.core.BasicPattern ;
import com.hp.hpl.jena.sparql.core.Var ;
import com.hp.hpl.jena.sparql.engine.QueryIterator ;
import com.hp.hpl.jena.sparql.engine.ResultSetStream ;
import com.hp.hpl.jena.sparql.engine.binding.Binding ;
import com.hp.hpl.jena.sparql.expr.E_LessThan ;
import com.hp.hpl.jena.sparql.expr.Expr ;
import com.hp.hpl.jena.sparql.expr.ExprVar ;
import com.hp.hpl.jena.sparql.expr.NodeValue ;
import com.hp.hpl.jena.sparql.util.FmtUtils ;

/** Build an algebra expression and execute it */

public class AlgebraExec
{
    public static void main (String[] argv)
    {
        String BASE = "http://example/" ;
        BasicPattern bp = new BasicPattern() ;
        Var var_x = Var.alloc("x") ;
        Var var_z = Var.alloc("z") ;
       
        // ---- Build expression
        bp.add(new Triple(var_x, Node.createURI(BASE+"p"), var_z)) ;
        Op op = new OpBGP(bp) ;
        //Expr expr = ExprUtils.parse("?z < 2 ") ;
        Expr expr = new E_LessThan(new ExprVar(var_z), NodeValue.makeNodeInteger(2)) ;
        op = OpFilter.filter(expr, op) ;

        // ---- Example setup
        Model m = makeModel() ;
        m.write(System.out, "TTL") ;
        System.out.println("--------------") ;
        System.out.print(op) ;
        System.out.println("--------------") ;

        // ---- Execute expression
        QueryIterator qIter = Algebra.exec(op, m.getGraph()) ;
       
        // -------- Either read the query iterator directly ...
        if ( false )
        {
            for ( ; qIter.hasNext() ; )
            {
                Binding b = qIter.nextBinding() ;
                Node n = b.get(var_x) ;
                System.out.println(FmtUtils.stringForNode(n)) ;
                System.out.println(b) ;
            }
            qIter.close() ;
        }
        else
        {
            // -------- Or make ResultSet from it (but not both - reading an
            //          iterator consumes the current solution)
            List<String> varNames = new ArrayList<String>() ;
            varNames.add("x") ;
            varNames.add("z") ;
            ResultSet rs = new ResultSetStream(varNames, m, qIter);
            ResultSetFormatter.out(rs) ;
            qIter.close() ;
        }
        System.exit(0) ;
    }

    private static Model makeModel()
    {
        String BASE = "http://example/" ;
        Model model = ModelFactory.createDefaultModel() ;
        model.setNsPrefix("", BASE) ;
        Resource r1 = model.createResource(BASE+"r1") ;
        Resource r2 = model.createResource(BASE+"r2") ;
        Property p1 = model.createProperty(BASE+"p") ;
        Property p2 = model.createProperty(BASE+"p2") ;
        RDFNode v1 = model.createTypedLiteral("1", XSDDatatype.XSDinteger) ;
        RDFNode v2 = model.createTypedLiteral("2", XSDDatatype.XSDinteger) ;
       
        r1.addProperty(p1, v1).addProperty(p1, v2) ;
        r1.addProperty(p2, v1).addProperty(p2, v2) ;
        r2.addProperty(p1, v1).addProperty(p1, v2) ;
       
        return model  ;
    }
}

/*
* (c) Copyright 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.
*/
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