/*
 * 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 opennlp.model;

/**
 * This interface allows one to implement a prior distribution for use in
 * maximum entropy model training.  
 * @author Tom Morton
 *
 */
public interface Prior {
  /**
   * Populates the specified array with the the log of the distribution for the specified context.  
   * The returned array will be overwritten and needs to be re-initialized with every call to this method.  
   * @param dist An array to be populated with the log of the prior distribution.
   * @param context The indices of the contextual predicates for an event.
   */
  public void logPrior(double[] dist, int[] context);
  
  /**
   * Populates the specified array with the the log of the distribution for the specified context.  
   * The returned array will be overwritten and needs to be re-initialized with every call to this method.  
   * @param dist An array to be populated with the log of the prior distribution.
   * @param context The indices of the contextual predicates for an event.
   * @param values The values associated with the context. 
   */
  public void logPrior(double[] dist, int[] context, float[] values);

  /**
   * Method to specify the label for the outcomes and contexts.  This is used to map 
   * integer outcomes and contexts to their string values.  This method is called prior
   * to any call to #logPrior.
   * @param outcomeLabels An array of each outcome label.
   * @param contextLabels An array of each context label.
   */
  public void setLabels(String[] outcomeLabels, String[] contextLabels);
}
