BinaryRelevanceModel.java

/* 
 * Copyright (C) 2015 Information Retrieval Group at Universidad Autónoma
 * de Madrid, http://ir.ii.uam.es
 *
 * This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/.
 */
package es.uam.eps.ir.ranksys.metrics.rel;

import es.uam.eps.ir.ranksys.core.preference.PreferenceData;
import java.util.Set;
import java.util.stream.Collectors;
import org.ranksys.core.util.tuples.Tuple2od;

/**
 * Relevance model in which the items in a preference subset with a value
 * equal or above a threshold are judged as relevant.
 *
 * @author Saúl Vargas (saul.vargas@uam.es)
 * @author Pablo Castells (pablo.castells@uam.es)
 * 
 * @param <U> type of the users
 * @param <I> type of the items
 */
public class BinaryRelevanceModel<U, I> extends IdealRelevanceModel<U, I> {

    private final PreferenceData<U, I> testData;
    private final double threshold;

    /**
     * Constructor
     *
     * @param caching are the user relevance models being cached?
     * @param testData test subset of the preferences
     * @param threshold relevance threshold
     */
    public BinaryRelevanceModel(boolean caching, PreferenceData<U, I> testData, double threshold) {
        super(caching, testData.getUsersWithPreferences());
        this.testData = testData;
        this.threshold = threshold;
    }

    @Override
    protected UserIdealRelevanceModel<U, I> get(U user) {
        return new UserBinaryRelevanceModel(user);
    }

    private class UserBinaryRelevanceModel implements UserIdealRelevanceModel<U, I> {

        private final Set<I> relevantItems;

        public UserBinaryRelevanceModel(U user) {
            this.relevantItems = testData.getUserPreferences(user)
                    .filter(iv -> iv.v2 >= threshold)
                    .map(Tuple2od::v1)
                    .collect(Collectors.toSet());
        }

        @Override
        public Set<I> getRelevantItems() {
            return relevantItems;
        }

        @Override
        public boolean isRelevant(I item) {
            return relevantItems.contains(item);
        }

        @Override
        public double gain(I item) {
            return isRelevant(item) ? 1.0 : 0.0;
        }

    }
}