SimpleTagger.java

package edu.northwestern.at.utils.corpuslinguistics.postagger.simple;

/*	Please see the license information at the end of this file. */

import java.util.*;

import edu.northwestern.at.utils.*;
import edu.northwestern.at.utils.corpuslinguistics.adornedword.*;
import edu.northwestern.at.utils.corpuslinguistics.postagger.*;
import edu.northwestern.at.utils.corpuslinguistics.tokenizer.*;

/**	Simple Part of Speech tagger.
 *
 *	<p>
 *	The simple part of speech tagger assigns a "noun" type
 *	part of speech to all words, except those that appear to
 *	be numbers.  Numbers are assigned a "number" part of speech.
 *	Words starting with a capital letter can be assigned a
 *	separate "proper name" part of speech.
 *	</p>
 *
 *	<p>
 *	This simple tagger is useful as a backup for a more
 *	sophisticated tagger when unknown words are encountered.
 *	</p>
 */

public class SimpleTagger extends AbstractPartOfSpeechTagger
	implements PartOfSpeechTagger, CanTagOneWord
{
	/**	Noun part of speech tag. */

	protected static String nounPOS;

	/**	Proper name part of speech tag. */

	protected static String namePOS;

	/**	Number part of speech tag. */

	protected static String numberPOS;

	/**	Create a simple tagger.
	 */

	public SimpleTagger()
	{
	}

	/**	Create a simple tagger.
	 *
	 *	@param	nounPOS		Part of speech for a noun.
	 *	@param	namePOS		Part of speech for a proper name.
	 *	@param	numberPOS	Part of speech tag for a number.
	 */

	public SimpleTagger
	(
		String nounPOS ,
		String namePOS ,
		String numberPOS
	)
	{
		this.nounPOS	= nounPOS;
		this.namePOS	= namePOS;
		this.numberPOS	= numberPOS;
	}

	/**	Tag a sentence.
	 *
	 *	@param	sentence	The sentence as an {@link edu.northwestern.at.utils.corpuslinguistics.adornedword.AdornedWord}
	 *
	 *	@return				The input List<AdornedWord> with its
	 *							words tagged with parts of speech.
	 */

	public<T extends AdornedWord> List<T> tagAdornedWordList
	(
		List<T> sentence
	)
	{
								//	Loop over words in sentence.

		for ( int i = 0 ; i < sentence.size() ; i++ )
		{
										//	Get next word.

			AdornedWord word	= sentence.get( i );

								//	Assign part of speech tag.

			tagWord( word );
		}
								//	Return tagged sentence.
		return sentence;
	}

	/**	Tag a single word.
	 *
	 *	@param	word	The word.
	 *
	 *	@return			The part of speech for the word.
	 */

	public String tagWord( String word )
	{
								//	Default tag is noun.

		String tag	= nounPOS;

								//	If word starts with a capital
								//	letter, assume it is a proper name.

		if ( Character.isUpperCase( word.charAt( 0 ) ) )
		{
			tag	= namePOS;
		}
								//	Check for number.

		if ( CharUtils.isNumber( word ) )
		{
			tag	= numberPOS;
		}
		else if ( CharUtils.isPunctuationOrSymbol( word ) )
		{
			tag	= word;
		}

		return tag;
	}

	/**	Tag a single adorned word.
	 *
	 *	@param	word	The adorned word.
	 *
	 *	@return			The adorned word with the part of speech
	 *					assigned.
	 */

	 public String tagWord( AdornedWord word )
	 {
	 	String tag	= tagWord( word.getSpelling() );

	 	word.setPartsOfSpeech( tag );

	 	return tag;
	 }

	/**	Return tagger description.
	 *
	 *	@return		Tagger description.
	 */

	public String toString()
	{
		return "Simple tagger";
	}
}

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   Northwestern University
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