/*
* 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 specific <em>basic model</em>
* implementations in the DFR framework. Basic models compute the
* <em>informative content Inf<sub>1</sub> = -log<sub>2</sub>Prob<sub>1</sub>
* </em>.
*
* @see DFRSimilarity
* @lucene.experimental
*/
public abstract class BasicModel {
/**
* Sole constructor. (For invocation by subclass
* constructors, typically implicit.)
*/
public BasicModel() {}
/** Returns the informative content score. */
public abstract float score(BasicStats stats, float tfn);
/**
* Returns an explanation for the score.
* <p>Most basic models use the number of documents and the total term
* frequency to compute Inf<sub>1</sub>. This method provides a generic
* explanation for such models. Subclasses that use other statistics must
* override this method.</p>
*/
public Explanation explain(BasicStats stats, float tfn) {
return Explanation.match(
score(stats, tfn),
getClass().getSimpleName() + ", computed from: ",
Explanation.match(stats.getNumberOfDocuments(), "numberOfDocuments"),
Explanation.match(stats.getTotalTermFreq(), "totalTermFreq"));
}
/**
* Subclasses must override this method to return the code of the
* basic model formula. Refer to the original paper for the list.
*/
@Override
public abstract String toString();
}