MetricNMPrecision.java

/*
 * ARX: Powerful Data Anonymization
 * Copyright 2012 - 2017 Fabian Prasser, Florian Kohlmayer and contributors
 * 
 * Licensed 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.deidentifier.arx.metric;

import org.deidentifier.arx.ARXConfiguration;
import org.deidentifier.arx.DataDefinition;
import org.deidentifier.arx.certificate.elements.ElementData;
import org.deidentifier.arx.framework.check.groupify.HashGroupify;
import org.deidentifier.arx.framework.check.groupify.HashGroupifyEntry;
import org.deidentifier.arx.framework.data.Data;
import org.deidentifier.arx.framework.data.DataManager;
import org.deidentifier.arx.framework.data.GeneralizationHierarchy;
import org.deidentifier.arx.framework.lattice.Transformation;

/**
 * This class provides an implementation of a weighted precision metric as 
 * proposed in: <br>
 * Sweeney, L. (2002). Achieving k-anonymity privacy protection using generalization and suppression.<br> 
 * International Journal of Uncertainty Fuzziness and, 10(5), 2002.<br>
 * <br>
 * This metric will respect attribute weights defined in the configuration.
 * 
 * @author Fabian Prasser
 * @author Florian Kohlmayer
 */
public class MetricNMPrecision extends MetricWeighted<InformationLossDefault> {

    /** SVUID. */
    private static final long serialVersionUID = -218192738838711533L;
    
    /** Height. */
    private int[]             height;
    
    /** Number of cells. */
    private double            cells;

    /**
     * Creates a new instance.
     */
    protected MetricNMPrecision() {
        super(true, false, false);
    }

    @Override
    public InformationLoss<?> createMaxInformationLoss() {
        return new InformationLossDefault(1);
    }

    @Override
    public InformationLoss<?> createMinInformationLoss() {
        return new InformationLossDefault(0);
    }

    @Override
    public ElementData render(ARXConfiguration config) {
        ElementData result = new ElementData("Precision");
        result.addProperty("Monotonic", this.isMonotonic(config.getMaxOutliers()));
        return result;
    }

    @Override
    public String toString() {
        return "Non-Monotonic Precision";
    }
    
    /**
     * Returns the number of cells.
     *
     * @return
     */
    protected double getCells() {
        return cells;
    }

    /**
     * @return the heights
     */
    protected int[] getHeights() {
        return height;
    }
    
    @Override
    protected InformationLossWithBound<InformationLossDefault> getInformationLossInternal(final Transformation node, final HashGroupify g) {
        
        int suppressedTuples = 0;
        int unsuppressedTuples = 0;
        
        HashGroupifyEntry m = g.getFirstEquivalenceClass();
        while (m != null) {
            // if (m.count > 0) is given implicitly
            unsuppressedTuples += m.isNotOutlier ? m.count : 0;
            suppressedTuples += m.isNotOutlier ? 0 : m.count;
            m = m.nextOrdered;
        }
        
        double precision = 0;
        for (int i = 0; i<height.length; i++) {
            double weight = weights != null ? weights[i] : 1d;
            double value = height[i] == 0 ? 0 : (double) node.getGeneralization()[i] / (double) height[i];
            precision += (double)unsuppressedTuples * value * weight;
            precision += (double)suppressedTuples * 1d * weight;
        }
        
        precision /= cells;
        
        // Return
        return new InformationLossDefaultWithBound(precision, getLowerBound(node).getValue());
    }

    @Override
    protected InformationLossWithBound<InformationLossDefault> getInformationLossInternal(Transformation node, HashGroupifyEntry entry) {
        return new InformationLossDefaultWithBound(entry.count, entry.count);
    }

    @Override
    protected InformationLossDefault getLowerBoundInternal(Transformation node) {
        double result = 0;
        final int[] transformation = node.getGeneralization();
        for (int i = 0; i < transformation.length; i++) {
            double weight = weights != null ? weights[i] : 1d;
            double level = (double) transformation[i];
            result += height[i] == 0 ? 0 : (level / (double) height[i]) * weight;
        }
        result /= (double) transformation.length;
        
        // Return
        return new InformationLossDefault(result);
    }
    
    @Override
    protected InformationLossDefault getLowerBoundInternal(Transformation node,
                                                           HashGroupify groupify) {
       return getLowerBoundInternal(node);
    }

    @Override
    protected void initializeInternal(final DataManager manager,
                                      final DataDefinition definition, 
                                      final Data input, 
                                      final GeneralizationHierarchy[] hierarchies, 
                                      final ARXConfiguration config) {
        super.initializeInternal(manager, definition, input, hierarchies, config);

        // Initialize maximum levels
        height = new int[hierarchies.length];
        for (int j = 0; j < height.length; j++) {
            height[j] = hierarchies[j].getArray()[0].length - 1;
        }
        
        int rowCount = super.getNumRecords(config, input);
        this.cells = (double)rowCount * (double)input.getHeader().length;
    }

}