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

  • Nested Class Summary

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

  • Constructor Summary

    Constructors
    Constructor
    Description
    Normalization()
    Sole constructor.

  • Method Summary

    Modifier and Type
    Method
    Description
    Explanation
    explain(BasicStats stats, double tf, double len)
    Returns an explanation for the normalized term frequency.
    abstract double
    tfn(BasicStats stats, double tf, double 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 Details

    • Normalization

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

  • Method Details

    • tfn

      public abstract double tfn(BasicStats stats, double tf, double len)
      Returns the normalized term frequency.
      Parameters:
      len - the field length.

    • explain

      public Explanation explain(BasicStats stats, double tf, double 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