org.terrier.matching
Class OldBasicMatching

java.lang.Object
  org.terrier.matching.OldBasicMatching

All Implemented Interfaces:

Matching

public class OldBasicMatching
extends java.lang.Object
implements Matching

This is the original matching implementation of Terrier. Performs the matching of documents with a query, by first assigning scores to documents for each query term and modifying these scores with the appropriate modifiers. Then, a series of document score modifiers are applied if necessary.

Author:

Vassilis Plachouras, Craig Macdonald

Field Summary

protected CollectionStatistics	collectionStatistics The collection statistics
protected java.util.ArrayList<DocumentScoreModifier>	documentModifiers Contains the document score modifiers to be applied for a query.
protected static java.lang.String	dsmNamespace The default namespace for the document score modifiers that are specified in the properties file.
protected static boolean	IGNORE_LOW_IDF_TERMS A property that enables to ignore the terms with a low IDF.
protected Index	index The index used for retrieval.
protected PostingIndex<BitIndexPointer>	invertedIndex The inverted file.
protected Lexicon<java.lang.String>	lexicon The lexicon used.
protected static org.apache.log4j.Logger	logger the logger for this class
protected static boolean	MATCH_EMPTY_QUERY A property that when it is true, it allows matching all documents to an empty query.
protected int	numberOfRetrievedDocuments The number of retrieved documents for a query.
protected ResultSet	resultSet The result set.
protected static int	RETRIEVED_SET_SIZE The maximum number of documents in the final retrieved set.

Constructor Summary

protected	OldBasicMatching()
	OldBasicMatching(Index _index) A default constructor that creates the CollectionResultSet and initialises the document and term modifier containers.

Method Summary

void	addDocumentScoreModifier(DocumentScoreModifier documentScoreModifier) Registers a document score modifier.
protected void	assignScores(int i, WeightingModel[] wModels, ResultSet rs, IterablePosting postings, LexiconEntry lEntry, double queryTermWeight) Assign scores method
DocumentScoreModifier	getDocumentScoreModifier(int i) Returns the i-th registered document score modifier.
java.lang.String	getInfo() Returns a descriptive string for the retrieval process performed.
ResultSet	getResultSet() Deprecated. match() now returns the ResultSet
protected void	initialise() Initialises the arrays prior of retrieval.
protected void	initialise(double[] scs) Initialises the arrays prior of retrieval, with the given scores.
protected void	initialiseDSMs()
ResultSet	match(java.lang.String queryNumber, MatchingQueryTerms queryTerms) Implements the matching of a query with the documents.
void	setCollectionStatistics(CollectionStatistics cs) Set the collection statistics.
void	setModel(Model model) Deprecated.

Methods inherited from class java.lang.Object

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

Field Detail

logger

protected static final org.apache.log4j.Logger logger

the logger for this class

dsmNamespace

protected static final java.lang.String dsmNamespace

The default namespace for the document score modifiers that are specified in the properties file.

See Also:

Constant Field Values

RETRIEVED_SET_SIZE

protected static int RETRIEVED_SET_SIZE

The maximum number of documents in the final retrieved set. It corresponds to the property matching.retrieved_set_size. The default value is 1000, however, setting the property to 0 will return all matched documents.

IGNORE_LOW_IDF_TERMS

protected static boolean IGNORE_LOW_IDF_TERMS

A property that enables to ignore the terms with a low IDF. In the match method, we check whether the frequency of a term in the collection is higher than the number of documents. If this is true, then by default we don't assign scores to documents that contain this term. We can change this default behaviour by altering the corresponding property ignore.low.idf.terms, the default value of which is true.

MATCH_EMPTY_QUERY

protected static boolean MATCH_EMPTY_QUERY

A property that when it is true, it allows matching all documents to an empty query. In this case the ordering of documents is random. More specifically, it is the ordering of documents in the document index. The corresponding property is match.empty.query and the default value is false.

numberOfRetrievedDocuments

protected int numberOfRetrievedDocuments

The number of retrieved documents for a query.

index

protected Index index

The index used for retrieval.

lexicon

protected Lexicon<java.lang.String> lexicon

The lexicon used.

invertedIndex

protected PostingIndex<BitIndexPointer> invertedIndex

The inverted file.

collectionStatistics

protected CollectionStatistics collectionStatistics

The collection statistics

resultSet

protected ResultSet resultSet

The result set.

documentModifiers

protected java.util.ArrayList<DocumentScoreModifier> documentModifiers

Contains the document score modifiers to be applied for a query.

Constructor Detail

OldBasicMatching

protected OldBasicMatching()

OldBasicMatching

public OldBasicMatching(Index _index)

A default constructor that creates the CollectionResultSet and initialises the document and term modifier containers.

Parameters:

_index - the object that encapsulates the basic data structures used for retrieval.

Method Detail

initialiseDSMs

protected void initialiseDSMs()

getResultSet

public ResultSet getResultSet()

Deprecated. match() now returns the ResultSet

Returns the result set.

initialise

protected void initialise()

Initialises the arrays prior of retrieval. Only the first time it is called, it will allocate memory for the arrays.

initialise

protected void initialise(double[] scs)

Initialises the arrays prior of retrieval, with the given scores. Only the first time it is called, it will allocate memory for the arrays.

Parameters:

scs - double[] the scores to initialise the result set with.

addDocumentScoreModifier

public void addDocumentScoreModifier(DocumentScoreModifier documentScoreModifier)

Registers a document score modifier. If more than one modifiers are registered, then they applied in the order they were registered.

Parameters:

documentScoreModifier - DocumentScoreModifier the score modifier to be applied.

getDocumentScoreModifier

public DocumentScoreModifier getDocumentScoreModifier(int i)

Returns the i-th registered document score modifier.

Returns:

the i-th registered document score modifier.

setModel

public void setModel(Model model)

Deprecated.

Sets the weighting model used for retrieval.

Parameters:

model - the weighting model used for retrieval

setCollectionStatistics

public void setCollectionStatistics(CollectionStatistics cs)

Set the collection statistics.

Specified by:

setCollectionStatistics in interface Matching

Parameters:

cs - CollectionStatistics to use during matching

getInfo

public java.lang.String getInfo()

Returns a descriptive string for the retrieval process performed.

Specified by:

getInfo in interface Matching

match

public ResultSet match(java.lang.String queryNumber,
                       MatchingQueryTerms queryTerms)
                throws java.io.IOException

Implements the matching of a query with the documents.

Specified by:

match in interface Matching

Parameters:

queryNumber - the identifier of the processed query.

queryTerms - the query terms to be processed.

Returns:

Returns the resultset expressed by this query.

Throws:

java.io.IOException - if a problem occurs during matching

assignScores

protected void assignScores(int i,
                            WeightingModel[] wModels,
                            ResultSet rs,
                            IterablePosting postings,
                            LexiconEntry lEntry,
                            double queryTermWeight)
                     throws java.io.IOException

Assign scores method

Parameters:

i - which query term is this

wModels - weighting models to use for this term

rs - Resultset to alter

postings - post list to process

lEntry - entry statistics

queryTermWeight - weight of the query term

Throws:

java.io.IOException