org.bibsonomy.webapp.util.RankingUtil.java Source code

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Here is the source code for org.bibsonomy.webapp.util.RankingUtil.java

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/**
 *
 *  BibSonomy-Webapp - The webapplication for Bibsonomy.
 *
 *  Copyright (C) 2006 - 2011 Knowledge & Data Engineering Group,
 *                            University of Kassel, Germany
 *                            http://www.kde.cs.uni-kassel.de/
 *
 *  This program is free software; you can redistribute it and/or
 *  modify it under the terms of the GNU General Public License
 *  as published by the Free Software Foundation; either version 2
 *  of the License, or (at your option) any later version.
 *
 *  This program is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License
 *  along with this program; if not, write to the Free Software
 *  Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
 */

package org.bibsonomy.webapp.util;

import java.util.HashMap;
import java.util.List;
import java.util.Map;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.bibsonomy.model.Post;
import org.bibsonomy.model.Resource;
import org.bibsonomy.model.Tag;

/**
 * Util class to compute ranking
 * 
 * @author dbenz
 * @version $Id: RankingUtil.java,v 1.5 2010-04-26 10:10:35 nosebrain Exp $
 */
public class RankingUtil {
    private static final Log LOGGER = LogFactory.getLog(RankingUtil.class);

    /**
     * the (rough) maximal global count of a tag (used to compute tf/idf-weighting)
     */
    private static int MAX_TAG_GLOBALCOUNT = 200000;

    /**
     * TODO: improve doc
     * 
     * @author dbenz
     */
    public enum RankingMethod {
        /**
         * TODO: improve doc
         */
        TAG_OVERLAP,

        /**
         * TODO: improve doc
         */
        TFIDF;
    }

    /**
     * Compute the ranking of a list of posts
     * 
     * @param <T>
     * @param sourceUserTags
     * @param targetUserTags
     * @param posts
     * @param rtype 
     * @param normalize 
     */
    public static <T extends Resource> void computeRanking(List<Tag> sourceUserTags, List<Tag> targetUserTags,
            List<Post<T>> posts, RankingMethod rtype, boolean normalize) {
        // first, build map of target user's tags
        Map<String, Integer> tagGlobalCounts = new HashMap<String, Integer>();
        Map<String, Integer> tagUserCounts = new HashMap<String, Integer>();
        int maxUserFreq = 0;
        for (Tag t : sourceUserTags) {
            if (t.getGlobalcount() > 0) {
                tagGlobalCounts.put(t.getName(), t.getGlobalcount());
            }
            tagUserCounts.put(t.getName(), t.getUsercount());
            if (t.getUsercount() > maxUserFreq) {
                maxUserFreq = t.getUsercount();
            }
        }
        // compute a ranking value for each post
        if (RankingMethod.TFIDF.equals(rtype)) {
            for (Post<T> post : posts) {
                for (Tag tag : post.getTags()) {
                    if (tagGlobalCounts.get(tag.getName()) != null && targetUserTags.contains(tag)) {
                        post.setRanking(
                                post.getRanking() + ((tagUserCounts.get(tag.getName()).doubleValue() / maxUserFreq)
                                        * Math.log(MAX_TAG_GLOBALCOUNT / tagGlobalCounts.get(tag.getName()))));
                    }
                }
                // normalize
                if (normalize) {
                    post.setRanking(post.getRanking() / post.getTags().size());
                }
            }
        }
        if (RankingMethod.TAG_OVERLAP.equals(rtype)) {
            for (Post<T> post : posts) {
                for (Tag tag : post.getTags()) {
                    if (tagGlobalCounts.get(tag.getName()) != null && targetUserTags.contains(tag)) {
                        post.setRanking(post.getRanking() + 1);
                    }
                }
                // normalize
                if (normalize) {
                    post.setRanking(post.getRanking() / post.getTags().size());
                }
            }
        }
    }

    /**
     * TODO: impove doc
     * 
     * @param <T>
     * @param sourceUserTags
     * @param targetUserTags
     */
    public static <T extends Resource> void computeRanking(List<Tag> sourceUserTags, List<Tag> targetUserTags) {
        // first, build map of target user's tags
        Map<String, Integer> tagGlobalCounts = new HashMap<String, Integer>();
        Map<String, Integer> tagUserCounts = new HashMap<String, Integer>();
        int maxUserFreq = 0;
        for (Tag t : sourceUserTags) {
            if (t.getGlobalcount() > 0) {
                tagGlobalCounts.put(t.getName(), t.getGlobalcount());
            }
            if (t.getUsercount() > 0) {
                tagUserCounts.put(t.getName(), t.getUsercount());
            }
            if (t.getUsercount() > maxUserFreq) {
                maxUserFreq = t.getUsercount();
            }
        }
        // compute the intersection of tags
        targetUserTags.retainAll(sourceUserTags);

        // compute the ranking for the intersection
        for (Tag tag : targetUserTags) {
            // double weight = ( ( ( (double) tagUserCounts.get(tag.getName()) ) / maxUserFreq ) * Math.log(MAX_TAG_GLOBALCOUNT / tagGlobalCounts.get(tag.getName()) ) ) * 100 ;
            tag.setGlobalcount(tag.getUsercount());
            LOGGER.debug("working on tag " + tag.getName() + ", having user freq "
                    + tagUserCounts.get(tag.getName()) + " and global count " + tagGlobalCounts.get(tag.getName()));
            if (tagUserCounts.get(tag.getName()) != null && tagGlobalCounts.get(tag.getName()) != null) {
                double weight = ((((double) tagUserCounts.get(tag.getName())) / maxUserFreq)
                        * Math.log(MAX_TAG_GLOBALCOUNT / tagGlobalCounts.get(tag.getName()))) * 10;
                // tag.setGlobalcount((int) weight);            
                tag.setUsercount((int) weight);
            } else {
                tag.setUsercount(0);
            }
        }

    }
}