org.apache.lucene.search.similarities

Class Normalization

java.lang.Object

org.apache.lucene.search.similarities.Normalization

Direct Known Subclasses:

Normalization.NoNormalization, NormalizationH1, NormalizationH2, NormalizationH3, NormalizationZ

public abstract class Normalization
extends Object

This class acts as the base class for the implementations of the term frequency normalization methods in the DFR framework.

See Also:

DFRSimilarity

WARNING: This API is experimental and might change in incompatible ways in the next release.

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	Normalization.NoNormalization Implementation used when there is no normalization.

Constructor Summary

Constructors

Constructor and Description
Normalization() Sole constructor.

Method Summary

Methods

Modifier and Type	Method and Description
Explanation	explain(BasicStats stats, float tf, float len) Returns an explanation for the normalized term frequency.
abstract float	tfn(BasicStats stats, float tf, float len) Returns the normalized term frequency.
abstract String	toString() Subclasses must override this method to return the code of the normalization formula.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Constructor Detail

Normalization

public Normalization()

Sole constructor. (For invocation by subclass constructors, typically implicit.)

Method Detail

tfn

public abstract float tfn(BasicStats stats,
        float tf,
        float len)

Returns the normalized term frequency.

Parameters:

len - the field length.

explain

public Explanation explain(BasicStats stats,
                  float tf,
                  float len)

Returns an explanation for the normalized term frequency.

The default normalization methods use the field length of the document and the average field length to compute the normalized term frequency. This method provides a generic explanation for such methods. Subclasses that use other statistics must override this method.

toString

public abstract String toString()

Subclasses must override this method to return the code of the normalization formula. Refer to the original paper for the list.

Overrides:

toString in class Object