This class implements the Bo1 scheme for query expansion. More...

Inheritance diagram for Xapian::Internal::Bo1EWeight:

Collaboration diagram for Xapian::Internal::Bo1EWeight:

Public Member Functions
	Bo1EWeight (const Xapian::Database &db_, Xapian::doccount rsize_, bool use_exact_termfreq_)
	Constructor. More...

double	get_weight () const
	Calculate the weight. More...

Public Member Functions inherited from Xapian::Internal::ExpandWeight
	ExpandWeight (const Xapian::Database &db_, Xapian::doccount rsize_, bool use_exact_termfreq_, bool want_collection_freq_)
	Constructor. More...

	ExpandWeight (const Xapian::Database &db_, Xapian::doccount rsize_, bool use_exact_termfreq_, bool want_collection_freq_, double expand_k_)
	Constructor. More...

void	collect_stats (TermList *merger, const std::string &term)
	Get the term statistics. More...

Additional Inherited Members
Protected Member Functions inherited from Xapian::Internal::ExpandWeight
double	get_avlen () const
	Return the average length of the database. More...

Xapian::doccount	get_rsize () const
	Return the number of documents in the RSet. More...

Xapian::termcount	get_collection_freq () const
	Return the collection frequency of the term. More...

Xapian::totallength	get_collection_len () const
	Return the length of the collection. More...

Xapian::doccount	get_dbsize () const
	Return the size of the database. More...

Protected Attributes inherited from Xapian::Internal::ExpandWeight
ExpandStats	stats
	An ExpandStats object to accumulate statistics. More...

Detailed Description

This class implements the Bo1 scheme for query expansion.

Bo1 is a representative scheme of the Divergence from Randomness Framework by Gianni Amati.

This is a parameter free weighting scheme for query expansion and it uses the Bose-Einstein probabilistic distribution.

For more information about the DFR Framework and the Bo1 scheme, please refer to Gianni Amati's PHD thesis.

Definition at line 255 of file expandweight.h.

Constructor & Destructor Documentation

Xapian::Internal::Bo1EWeight::Bo1EWeight	(	const Xapian::Database &	db_,
		Xapian::doccount	rsize_,
		bool	use_exact_termfreq_
	)

inline

Constructor.

Parameters

db_	The database.
rsize_	The number of documents in the RSet.
use_exact_termfreq_	When expanding over a combined database, should we use the exact termfreq (if false a cheaper approximation is used).

All the parameters are passed to the parent ExpandWeight object.

Definition at line 267 of file expandweight.h.

double Xapian::Internal::Bo1EWeight::get_weight ( ) const

virtual

Calculate the weight.

Definition at line 33 of file bo1eweight.cc.

References log2().

The documentation for this class was generated from the following files: