org.apache.clerezza.utils.SeeAlsoExpander Maven / Gradle / Ivy

Go to download
/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor  license  agreements.  See the NOTICE file distributed
 * with this work  for  additional  information  regarding  copyright
 * ownership.  The ASF  licenses  this file to you under  the  Apache
 * License, Version 2.0 (the "License"); you may not  use  this  file
 * except in compliance with the License.  You may obtain  a copy  of
 * the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless  required  by  applicable law  or  agreed  to  in  writing,
 * software  distributed  under  the  License  is  distributed  on an
 * "AS IS"  BASIS,  WITHOUT  WARRANTIES  OR  CONDITIONS  OF ANY KIND,
 * either  express  or implied.  See  the License  for  the  specific
 * language governing permissions and limitations under  the License.
 */
package org.apache.clerezza.utils;

import org.apache.clerezza.IRI;
import org.apache.clerezza.RDFTerm;
import org.apache.clerezza.Graph;
import org.apache.clerezza.dataset.NoSuchEntityException;
import org.apache.clerezza.dataset.TcManager;
import org.apache.clerezza.ontologies.RDFS;

import java.util.HashSet;
import java.util.Iterator;
import java.util.Set;
import java.util.concurrent.locks.Lock;

/**
 * Expands a GraphNode expanding SeeAlso-References of the node.
 *
 * @author reto
 */
public class SeeAlsoExpander {
    /**
     * using TcManger instead of TcProvider as this ensures LockableGraphs
     */
    private final TcManager tcManager;

    public SeeAlsoExpander(TcManager tcManager) {
        this.tcManager = tcManager;
    }

    /**
     * expands a node dereferencing its rdfs:seeAlso references using the
     * tcManager associated to this instance. If the added TripleCollections
     * also associate rdfs:seeAlso properties to node this are expanded till
     * the maximum recursion depth specified.
     *
     * @param node      the node to be expanded
     * @param recursion the maximum recursion depth
     * @return a new GraphNode over the union of the original and all expansion graphs
     */
    public GraphNode expand(GraphNode node, int recursion) {
        Set alreadyVisited = new HashSet();
        Set resultTripleCollections = new HashSet();
        resultTripleCollections.add(node.getGraph());
        for (IRI uriRef : expand(node, alreadyVisited, recursion)) {
            try {
                resultTripleCollections.add(tcManager.getGraph(uriRef));
            } catch (NoSuchEntityException e) {
                //ignore
            }
        }
        return new GraphNode(node.getNode(),
                new UnionGraph(resultTripleCollections.toArray(
                        new Graph[resultTripleCollections.size()])));
    }

    private Set getSeeAlsoObjectUris(GraphNode node) {
        Set result = new HashSet();
        Lock l = node.readLock();
        l.lock();
        try {
            Iterator objects = node.getObjects(RDFS.seeAlso);
            while (objects.hasNext()) {
                RDFTerm next = objects.next();
                if (next instanceof IRI) {
                    result.add((IRI) next);
                }
            }
        } finally {
            l.unlock();
        }
        return result;
    }

    private Set expand(GraphNode node, Set alreadyVisited, int recursion) {
        Set rdfSeeAlsoTargets = getSeeAlsoObjectUris(node);
        Set result = new HashSet();
        result.addAll(rdfSeeAlsoTargets);
        recursion++;
        if (recursion > 0) {
            rdfSeeAlsoTargets.removeAll(alreadyVisited);
            alreadyVisited.addAll(rdfSeeAlsoTargets);
            for (IRI target : rdfSeeAlsoTargets) {
                try {
                    result.addAll(expand(new GraphNode(node.getNode(),
                            tcManager.getGraph(target)), alreadyVisited, recursion));
                } catch (NoSuchEntityException e) {
                    //ignore
                }
            }
        }
        return result;
    }

}