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/*
 * SimMetrics - SimMetrics is a java library of Similarity or Distance Metrics,
 * e.g. Levenshtein Distance, that provide float based similarity measures
 * between String Data. All metrics return consistent measures rather than
 * unbounded similarity scores.
 * 
 * Copyright (C) 2014 SimMetrics authors
 * 
 * This file is part of SimMetrics. 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 3 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
 * SimMetrics. If not, see .
 */

package org.simmetrics;

import java.util.Collections;
import java.util.Set;

/**
 * Measures the similarity between two arbitrary sets containing elements of the
 * same type. The measurement results in a value between 0 and 1 inclusive. A
 * value of zero indicates that the sets are dissimilar, a value of 1 indicates
 * they are similar.
 * 
 * 
 * The elements in the set have to implement {@link Object#hashCode()} and
 * {@link Object#equals(Object)}.The similarity measure should be consistent
 * with equals such that {@code a.equals(b) => compare(a,b) == 1.0}.
 * Implementations may not modify the contents of the set. Sets should be
 * treated as if wrapped by {@link Collections#unmodifiableSet(Set)}.
 * 
 * 
 * @param 
 *            the type of elements contained in the sets
 *
 */
public interface SetMetric extends Metric> {
	/**
	 * Measures the similarity between sets a and b. The measurement results in
	 * a value between 0 and 1 inclusive. A value of zero indicates that the
	 * sets are dissimilar, a value of 1 indicates they are similar.
	 * 
	 * @param a
	 *            set a to compare
	 * @param b
	 *            set b to compare
	 * @return a value between 0 and 1 inclusive indicating similarity
	 */
	public float compare(Set a, Set b);

}