org.apache.solr.search.similarities

Class DFRSimilarityFactory

java.lang.Object

org.apache.solr.schema.SimilarityFactory

org.apache.solr.search.similarities.DFRSimilarityFactory

public class DFRSimilarityFactory
extends SimilarityFactory

Factory for DFRSimilarity

You must specify the implementations for all three components of DFR (strings). In general the models are parameter-free, but two of the normalizations take floating point parameters (see below):

1. basicModel: Basic model of information content:
   • Be: Limiting form of Bose-Einstein
   • G: Geometric approximation of Bose-Einstein
   • P: Poisson approximation of the Binomial
   • D: Divergence approximation of the Binomial
   • I(n): Inverse document frequency
   • I(ne): Inverse expected document frequency [mixture of Poisson and IDF]
   • I(F): Inverse term frequency [approximation of I(ne)]
2. afterEffect: First normalization of information gain:
   • L: Laplace's law of succession
   • B: Ratio of two Bernoulli processes
   • none: no first normalization
3. normalization: Second (length) normalization:
   • H1: Uniform distribution of term frequency
     • parameter c (float): hyper-parameter that controls the term frequency normalization with respect to the document length. The default is 1
   • H2: term frequency density inversely related to length
     • parameter c (float): hyper-parameter that controls the term frequency normalization with respect to the document length. The default is 1
   • H3: term frequency normalization provided by Dirichlet prior
     • parameter mu (float): smoothing parameter μ. The default is 800
   • Z: term frequency normalization provided by a Zipfian relation
     • parameter z (float): represents A/(A+1) where A measures the specificity of the language. The default is 0.3
   • none: no second normalization

Optional settings:

• discountOverlaps (bool): Sets SimilarityBase.setDiscountOverlaps(boolean)

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

Field Summary

Fields inherited from class org.apache.solr.schema.SimilarityFactory

CLASS_NAME, params

Constructor Summary

Constructors

Constructor and Description
DFRSimilarityFactory()

Method Summary

Methods

Modifier and Type	Method and Description
Similarity	getSimilarity()
void	init(SolrParams params)

Methods inherited from class org.apache.solr.schema.SimilarityFactory

getClassArg, getNamedPropertyValues, getParams

Methods inherited from class java.lang.Object

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

Constructor Detail

DFRSimilarityFactory

public DFRSimilarityFactory()

Method Detail

init

public void init(SolrParams params)

Overrides:

init in class SimilarityFactory

getSimilarity

public Similarity getSimilarity()

Specified by:

getSimilarity in class SimilarityFactory