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Apache Lucene (module: classification)
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/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You 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.apache.lucene.classification;

import java.io.IOException;
import java.util.List;

/**
 * A classifier, see http://en.wikipedia.org/wiki/Classifier_(mathematics), which
 * assign classes of type T
 *
 * @lucene.experimental
 */
public interface Classifier {

  /**
   * Assign a class (with score) to the given text String
   *
   * @param text a String containing text to be classified
   * @return a {@link ClassificationResult} holding assigned class of type T and score
   * @throws IOException If there is a low-level I/O error.
   */
  ClassificationResult assignClass(String text) throws IOException;

  /**
   * Get all the classes (sorted by score, descending) assigned to the given text String.
   *
   * @param text a String containing text to be classified
   * @return the whole list of {@link ClassificationResult}, the classes and scores. Returns 
   *     null if the classifier can't make lists.
   * @throws IOException If there is a low-level I/O error.
   */
  List> getClasses(String text) throws IOException;

  /**
   * Get the first max classes (sorted by score, descending) assigned to the given text
   * String.
   *
   * @param text a String containing text to be classified
   * @param max the number of return list elements
   * @return the whole list of {@link ClassificationResult}, the classes and scores. Cut for "max"
   *     number of elements. Returns null if the classifier can't make lists.
   * @throws IOException If there is a low-level I/O error.
   */
  List> getClasses(String text, int max) throws IOException;
}