1 /*
2 * Licensed to the Apache Software Foundation (ASF) under one or more
3 * contributor license agreements. See the NOTICE file distributed with
4 * this work for additional information regarding copyright ownership.
5 * The ASF licenses this file to You under the Apache License, Version 2.0
6 * (the "License"); you may not use this file except in compliance with
7 * the License. You may obtain a copy of the License at
8 *
9 * http://www.apache.org/licenses/LICENSE-2.0
10 *
11 * Unless required by applicable law or agreed to in writing, software
12 * distributed under the License is distributed on an "AS IS" BASIS,
13 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14 * See the License for the specific language governing permissions and
15 * limitations under the License.
16 */
17
18 package org.apache.commons.text.similarity;
19
20 import java.util.function.BiFunction;
21
22 /**
23 * Scores the similarity between two {@link Object}s of the same type.
24 *
25 * <p>
26 * A string similarity score is intended to have <em>some</em> of the properties of a metric, yet allowing for exceptions, like the Jaro-Winkler similarity
27 * score.
28 * </p>
29 * <p>
30 * A similarity score is the function {@code d: [X * X] -> [0, INFINITY)} with the following properties:
31 * </p>
32 * <ul>
33 * <li>{@code d(x,y) >= 0}, non-negativity or separation axiom</li>
34 * <li>{@code d(x,y) == d(y,x)}, symmetry.</li>
35 * </ul>
36 *
37 * <p>
38 * Notice, these are two of the properties that contribute to {@code d} being a metric.
39 * </p>
40 *
41 * @param <T> Input type
42 * @param <R> The type of similarity score unit used by this score.
43 * @since 1.13.0
44 */
45 public interface ObjectSimilarityScore<T, R> extends BiFunction<T, T, R> {
46
47 /**
48 * Compares two Objects.
49 *
50 * @param left the "left" or "first" input.
51 * @param right the "right" or "second" input.
52 * @return The similarity score between two Objects.
53 */
54 @Override
55 R apply(T left, T right);
56
57 }