/*
 * 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.samoa.moa.classifiers;

import org.apache.samoa.instances.Instance;
import org.apache.samoa.moa.core.Example;
import org.apache.samoa.moa.learners.Learner;

/**
 * Classifier interface for incremental classification models.
 * 
 * @author Richard Kirkby (rkirkby@cs.waikato.ac.nz)
 * @version $Revision: 7 $
 */
public interface Classifier extends Learner<Example<Instance>> {

  /**
   * Gets the classifiers of this ensemble. Returns null if this learner is a single learner.
   * 
   * @return an array of the learners of the ensemble
   */
  public Classifier[] getSubClassifiers();

  /**
   * Produces a copy of this learner.
   * 
   * @return the copy of this learner
   */
  public Classifier copy();

  /**
   * Gets whether this classifier correctly classifies an instance. Uses getVotesForInstance to obtain the prediction
   * and the instance to obtain its true class.
   * 
   * 
   * @param inst
   *          the instance to be classified
   * @return true if the instance is correctly classified
   */
  public boolean correctlyClassifies(Instance inst);

  /**
   * Trains this learner incrementally using the given example.
   * 
   * @param inst
   *          the instance to be used for training
   */
  public void trainOnInstance(Instance inst);

  /**
   * Predicts the class memberships for a given instance. If an instance is unclassified, the returned array elements
   * must be all zero.
   * 
   * @param inst
   *          the instance to be classified
   * @return an array containing the estimated membership probabilities of the test instance in each class
   */
  public double[] getVotesForInstance(Instance inst);
}