org.simmetrics.Metric Maven / Gradle / Ivy
/*
* #%L
* Simmetrics Core
* %%
* Copyright (C) 2014 - 2016 Simmetrics Authors
* %%
* 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.
* #L%
*/
package org.simmetrics;
/**
* Measures the similarity between two arbitrary objects 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 similarity measure should be consistent with equals such that
* {@code a.equals(b) => compare(a,b) == 1.0}.
*
* The similarity measure should be reflexive such that
* {@code compare(a,a) == 1.0}.
*
* The similarity measure should be symmetric such that
* {@code compare(a,b) == compare(b,a)}.
*
* The similarity measure may be transitive such that
* {@code 1.0 - compare(a, c) ≤ 1.0 - compare(a, b) + 1.0 - compare(b, c)}
*
* The similarity measure may satisfy the coincidence axiom such that
* {@code compare(a, b) = 0 if and only if a.equals(b)}
*
* Implementations may not modify the arguments. Arguments should be treated as
* if they were unmodifiable.
*
* @see Wikipedia -
* Metric
*
* @param
* type of the elements compared
*
*/
public interface Metric {
/**
* Measures the similarity between a and b. The measurement results in a
* value between 0 and 1 inclusive. A value of {@code 0.0} indicates that
* {@code a} and {@code b} are dissimilar, a value of {@code 1.0} indicates
* they are similar.
*
* @param a
* object a to compare
* @param b
* object b to compare
* @return a value between 0 and 1 inclusive indicating similarity
* @throws NullPointerException
* when either a or b is null
*/
public float compare(T a, T b);
}