A worker that computes the stems of words. For example, the French word "couvent" is both a singular noun and the third person plural form of the verb "couver". Thus, a French ULStemmer object would identify both "couvent n.m." and "couver v." as stems for "couvent". More...

#include <ulstemmer.h>

Public Member Functions
	ULStemmer ()

	ULStemmer (const ULStemmer &other)

virtual	~ULStemmer ()

ULStemmer &	operator= (const ULStemmer &other)

void	clear ()

ULDissector *	getDissector ()

void	setDissector (ULDissector *newDissector)

const ULLanguage &	getLanguage () const

virtual bool	isServiceAvailable (const ULServiceDescriptor &service)

virtual void	getAvailableServices (ULList< ULServiceDescriptor > &services)

virtual void	setCancelOperation (bool shouldCancel)

ULError	getAllStems (const ULString &surfaceForm, ULList< ULDerivation > &stemList)

ULError	getStems (const ULString &surfaceForm, ULList< ULDerivation > &stemList)

ULError	getStems (const ULString &surfaceForm, const ULPartOfSpeechCategory &category, ULList< ULDerivation > &stemList)

ULError	getFrequencies (const ULString &surfaceForm, ULList< ULFrequency > &frequencyList)

Public Member Functions inherited from ULWorker
	ULWorker ()

virtual	~ULWorker ()

virtual bool	shouldCancelOperation () const

Detailed Description

A worker that computes the stems of words. For example, the French word "couvent" is both a singular noun and the third person plural form of the verb "couver". Thus, a French ULStemmer object would identify both "couvent n.m." and "couver v." as stems for "couvent".

Constructor & Destructor Documentation

ULStemmer::ULStemmer ( )

Default constructor.

ULStemmer::ULStemmer ( const ULStemmer & other )

Copy constructor.

ULStemmer::~ULStemmer ( )

virtual

Destructor

Member Function Documentation

void ULStemmer::clear ( )

Sets this stemmer to its default state.

ULError ULStemmer::getAllStems	(	const ULString &	surfaceForm,
		ULList< ULDerivation > &	stemList
	)

Computes the full list of stems for the specified surface form. For example, if the surface form is "thought", then the stem list will include (thought, thought, noun), (thought, think, verb, past participle), (thought, think, verb, past tense, first person singular), (thought, think, verb, past tense, second person singular), etc.

This list can get long, since some surface forms will play many roles for the same root word (as "thought" does for the verb "think"). To get the list of distinct root words without the repetition (e.g. only one stem for (thought, think, verb)), use getStems instead of getAllStems.

Returns: ULError::NoError if the stemming operation completes successfully, ULError::NoMatch if there are no suitable stems, or some other ULError value

Parameters

[in]	surfaceForm	The word whose stems are sought.
[in]	stemList	The list of stems.

void ULStemmer::getAvailableServices ( ULList< ULServiceDescriptor > & serviceList )

virtual

Parameters

[out] serviceList Used to return a list of all the services this ULWorker can provide.

Implements ULWorker.

ULDissector * ULStemmer::getDissector ( )

Returns: a pointer to the ULDissector used by this stemmer to perform stemming operations.

ULError ULStemmer::getFrequencies	(	const ULString &	surfaceForm,
		ULList< ULFrequency > &	frequencyList
	)

ULLanguageDataSource objects may contain frequency data of the form (word, root, part-of-speech, count). These data come from manually tagged corpora similar to the American National Corpus or the Penn Treebank.

This method returns a list of frequency objects corresponding to the specified word. (For example, the word "chairs" might yield ("chairs", "chair", verb, 21), ("chairs", "chair", noun, 623), and ("chairs", "chair", unknown, 2).

The method performs its search in a case-insensitive and accent-insensitive way.

Returns: ULError::NoMatch if there are no frequency records corresponding to the specified word, ULError::DataSourceOpenFailed if there was a problem with the data source, or ULError::NoError otherwise.

Parameters

[in]	word	the word whose frequencies are sought
[out]	frequencyList	the corresponding frequencies, sorted in decreasing order of frequency

const ULLanguage & ULStemmer::getLanguage ( ) const

Returns: the language for which this stemmer can compute stems.

ULError ULStemmer::getStems	(	const ULString &	surfaceForm,
		ULList< ULDerivation > &	stemList
	)

Computes the list of root words for the specified surface form. For example, if the surface form is "thought", then the stem list will consist of (thought, thought, noun) and (thought, think, verb). Note that unlike getAllStems, this method returns exactly one ULDerivation object per root word, and is thus usually more useful and easier to use than getAllStems.

Returns: ULError::NoError if the stemming operation completes successfully, ULError::NoMatch if there are no suitable stems, or some other ULError value otherwise.

Parameters

[in]	surfaceForm	The word whose stems are sought.
[in]	stemList	The list of stems.

ULError ULStemmer::getStems	(	const ULString &	surfaceForm,
		const ULPartOfSpeechCategory &	category,
		ULList< ULDerivation > &	stemList
	)

Computes the list of root words for the specified surface form, restricted to the specified part of speech category. For example, if the surface form is "thought" and the category is verb, then the stem list will consist of only (thought, think, verb). Note that unlike getAllStems, this method returns exactly one ULDerivation object per root word.

Note that the part of speech category restriction applies to the surface form, not necessarily to the root. For example, the surface form "baker" is a noun, but it can be stemmed to the root "bake", which is a verb. If we call getStems("baker", ULPartOfSpeechCategory::Verb, stemList), we will get no results, since "baker" is not a verb. If we call getStems("baker", ULPartOfSpeechCategory::Noun, stemList), however, we will get the verb "bake" as our stem.

Returns: ULError::NoError if the stemming operation completes successfully, ULError::NoMatch if there are no suitable stems, or some other ULError value otherwise.

Parameters

[in]	surfaceForm	The word whose stems are sought.
[in]	category	The desired part of speech category.
[in]	stemList	The list of stems.

bool ULStemmer::isServiceAvailable ( const ULServiceDescriptor & service )

virtual

Returns: true if the specified service can be performed by this ULWorker, and false otherwise.

Parameters

service The desired service.

Implements ULWorker.

ULStemmer & ULStemmer::operator= ( const ULStemmer & other )

Assignment operator.

void ULStemmer::setCancelOperation ( bool shouldCancel )

virtual

Setter for the long-operation cancellation boolean attribute.

Parameters

[in] set to true if

Reimplemented from ULWorker.

void ULStemmer::setDissector ( ULDissector * newDissector )

Sets the ULDissector to be used by this stemmer to perform stemming operations. This ULStemmer does not take responsibility for deleting the dissector. That will need to happen elsewhere (typically the ULFactory will take care of it if your application uses ULFactory to instantiate data sources and workers). param[in] newDissector A pointer to the desired dissector.

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

ulstemmer.h
ulstemmer.cpp

Public Member Functions

Detailed Description

Constructor & Destructor Documentation

Member Function Documentation