http://lucene.apache.org/lucene-parent/lucene-core: Apache Lucene Java Core (The Apache Software Foundation) 
/*
 * 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.search.similarities;


import org.apache.lucene.search.Explanation;


This class acts as the base class for the implementations of the first
normalization of the informative content in the DFR framework. This
component is also called the after effect and is defined by the
formula Inf2 = 1 - Prob2, where
Prob2 measures the information gain.

See Also:
  • DFRSimilarity
@lucene.experimental
/**
 * This class acts as the base class for the implementations of the <em>first
 * normalization of the informative content</em> in the DFR framework. This
 * component is also called the <em>after effect</em> and is defined by the
 * formula <em>Inf<sub>2</sub> = 1 - Prob<sub>2</sub></em>, where
 * <em>Prob<sub>2</sub></em> measures the <em>information gain</em>.
 * 
 * @see DFRSimilarity
 * @lucene.experimental
 */
public abstract class AfterEffect {
  
  
Sole constructor. (For invocation by subclass 
constructors, typically implicit.)

/**
   * Sole constructor. (For invocation by subclass 
   * constructors, typically implicit.)
   */
  public AfterEffect() {}

  
Returns the product of the after effect with 1+tfn. This may not depend on the value of tfn. 
/** Returns the product of the after effect with {@code 1+tfn}.
   *  This may not depend on the value of {@code tfn}. */
  public abstract double scoreTimes1pTfn(BasicStats stats);
  
  
Returns an explanation for the score. 
/** Returns an explanation for the score. */
  public abstract Explanation explain(BasicStats stats, double tfn);
  
  
Subclasses must override this method to return the code of the
after effect formula. Refer to the original paper for the list. 

/**
   * Subclasses must override this method to return the code of the
   * after effect formula. Refer to the original paper for the list. 
   */
  @Override
  public abstract String toString();
}