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OmWeight Class Reference

Abstract base class for weighting schemes. More...

#include <omenquire.h>

Inheritance diagram for OmWeight:

BM25Weight BoolWeight TradWeight List of all members.

Public Methods

 OmWeight ()
virtual ~OmWeight ()
OmWeight * create (const Internal *internal_, om_doclength querysize_, om_termcount wqf_, om_termname tname_)
 Initialise the weight object with the neccessary stats, or places to get them from. More...

virtual om_weight get_sumpart (om_termcount wdf, om_doclength len) const=0
 Get a weight which is part of the sum over terms being performed. More...

virtual om_weight get_maxpart () const=0
 Gets the maximum value that get_sumpart() may return. More...

virtual om_weight get_sumextra (om_doclength len) const=0
 Get an extra weight for a document to add to the sum calculated over the query terms. More...

virtual om_weight get_maxextra () const=0
 Gets the maximum value that get_sumextra() may return. More...

virtual bool get_sumpart_needs_doclength () const
 return false if the weight object doesn't need doclength. More...


Protected Attributes

const Internal * internal
om_doclength querysize
om_termcount wqf
om_termname tname

Friends

class OmEnquire

Detailed Description

Abstract base class for weighting schemes.


Member Function Documentation

OmWeight* OmWeight::create const Internal *    internal_,
om_doclength    querysize_,
om_termcount    wqf_,
om_termname    tname_
[inline]
 

Initialise the weight object with the neccessary stats, or places to get them from.

You shouldn't call this method yourself

Parameters:
internal_  Object to ask for collection statistics.
querysize_  Query size.
wqf_  Within query frequency of term this object is associated with.
tname_  Term which this object is associated with.

virtual om_weight OmWeight::get_maxextra   const [pure virtual]
 

Gets the maximum value that get_sumextra() may return.

This is used in optimising searches.

Implemented in BoolWeight, BM25Weight, and TradWeight.

virtual om_weight OmWeight::get_maxpart   const [pure virtual]
 

Gets the maximum value that get_sumpart() may return.

This is used in optimising searches, by having the postlist tree decay appropriately when parts of it can have limited, or no, further effect.

Implemented in BoolWeight, BM25Weight, and TradWeight.

virtual om_weight OmWeight::get_sumextra om_doclength    len const [pure virtual]
 

Get an extra weight for a document to add to the sum calculated over the query terms.

This returns a weight for a given document, and is used by some weighting schemes to account for influence such as document length.

Parameters:
len  the (unnormalised) document length.

Implemented in BoolWeight, BM25Weight, and TradWeight.

virtual om_weight OmWeight::get_sumpart om_termcount    wdf,
om_doclength    len
const [pure virtual]
 

Get a weight which is part of the sum over terms being performed.

This returns a weight for a given term and document. These weights are summed to give a total weight for the document.

Parameters:
wdf  the within document frequency of the term.
len  the (unnormalised) document length.

Implemented in BoolWeight, BM25Weight, and TradWeight.

virtual bool OmWeight::get_sumpart_needs_doclength   const [inline, virtual]
 

return false if the weight object doesn't need doclength.

Reimplemented in BoolWeight, BM25Weight, and TradWeight.


The documentation for this class was generated from the following file:
Documentation for Xapian (version 0.6.1).
Generated on 7 Dec 2002 by Doxygen 1.2.15.