emolib.pos
Class POSTagger

java.lang.Object
  emolib.util.proc.TextDataProcessor
      emolib.pos.POSTagger

All Implemented Interfaces:

Configurable, DataProcessor

Direct Known Subclasses:

EnglishStanford, SpanishQTag

public abstract class POSTagger
extends TextDataProcessor

The POSTagger abstract class defines the general structure to perform the Part-Of-Speech (POS) tagging process, which determines the correct function of a word in a sentence.

Nouns, adjectives and verbs share the same regular expression, thus their function cannot be inferred with a simple tokeniser. These classes of word need to be disambiguated according to the context where they appear.

In order to overcome this problem, two approaches can be presented:

• Rule-based approaches: The classical approach to resolving ambiguities by constructing a set of rules based on contextual clues. Many rules and exceptions are required, and this labour is hard and tedious to accomplish and maintain.
• Statistical approaches: The construction of these rules is based on the estimation of the conditional probabilities of appearance of a word according to the context observed in previously tagged textual corpora.

Any well coded POS tagger should set the incoming words as nouns, verbs or adjectives according to the results obtained.

Author:

Alexandre Trilla (atrilla@salle.url.edu)

Constructor Summary

POSTagger()
Main constructor of the POSTagger.

Method Summary

abstract void	applyPOSTagging(TextData inputTextDataObject) Method to perform the POS tagging process.
Data	getData() Obtains the TextData from the previous module, processes it and makes it available to the rest of the text processing chain.
void	initialize() Method to initialize the POSTagger.
void	newProperties(PropertySheet ps) This method is called when this configurable component has new data.
void	register(java.lang.String name, Registry registry) Register my properties.

Methods inherited from class emolib.util.proc.TextDataProcessor

flush, getName, getPredecessor, setPredecessor, toString

Methods inherited from class java.lang.Object

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

Constructor Detail

POSTagger

public POSTagger()

Main constructor of the POSTagger.

Method Detail

register

public void register(java.lang.String name,
                     Registry registry)
              throws PropertyException

Description copied from interface: Configurable

Register my properties. This method is called once early in the time of the component, shortly after the component is constructed. This component should register any configuration properties that it needs to register. If this configurable extends another configurable, super.register should also be called

Specified by:

register in interface Configurable

Overrides:

register in class TextDataProcessor

Parameters:

name - the name of the component

registry - the registry for this component

Throws:

PropertyException

newProperties

public void newProperties(PropertySheet ps)
                   throws PropertyException

Description copied from interface: Configurable

This method is called when this configurable component has new data. The component should first validate the data. If it is bad the component should return false. If the data is good, the component should record the the data internally and return true.

Specified by:

newProperties in interface Configurable

Overrides:

newProperties in class TextDataProcessor

Parameters:

ps - a property sheet holding the new data

Throws:

PropertyException - if there is a problem with the properties.

getData

public Data getData()
             throws DataProcessingException

Obtains the TextData from the previous module, processes it and makes it available to the rest of the text processing chain.

Specified by:

getData in interface DataProcessor

Specified by:

getData in class TextDataProcessor

Returns:

The next available Data object, returns null if no Data object is available.

Throws:

DataProcessingException - If there is a processing error.

initialize

public void initialize()

Method to initialize the POSTagger.

Specified by:

initialize in interface DataProcessor

Overrides:

initialize in class TextDataProcessor

applyPOSTagging

public abstract void applyPOSTagging(TextData inputTextDataObject)

Method to perform the POS tagging process.

Parameters:

inputTextDataObject - The TextData object to process.