package edu.northwestern.at.utils.corpuslinguistics.tokenizer;
/* Please see the license information at the end of this file. */
import java.util.*;
import edu.northwestern.at.utils.ListFactory;
import edu.northwestern.at.utils.PatternReplacer;
/** Split text into tokens according the Penn Treebank tokenization rules.
*
* <p>
* Based upon the sed script written by Robert McIntyre at
* http://www.cis.upenn.edu/~treebank/tokenizer.sed .
* </p>
*/
public class PennTreebankTokenizer
extends AbstractWordTokenizer
implements WordTokenizer
{
/** Replacement patterns for transforming original text. */
protected static List<PatternReplacer> pennPatterns =
ListFactory.createNewList();
/** Create a simple word tokenizer.
*/
public PennTreebankTokenizer()
{
}
public static String prepareTextForTokenization( String s )
{
for ( int i = 0 ; i < pennPatterns.size() ; i++ )
{
s = pennPatterns.get( i ).replace( s );
}
return s.trim();
}
/** Break text into word tokens.
*
* @param text Text to break into word tokens.
*
* @return List of word tokens.
*
* <p>
* Word tokens may be words, numbers, punctuation, etc.
* </p>
*/
public List<String> extractWords( String text )
{
// Holds listof tokenized words.
List<String> result = ListFactory.createNewList();
// Prepare text for tokenization
// by splitting words and punctuation
// according to Penn Treebank rules.
String fixedText = prepareTextForTokenization( text );
// All we have to do now is pick
// up the individual "words" which
// are separated by one or more blanks.
// Use a StringTokenizer for this.
StringTokenizer tokenizer = new StringTokenizer( fixedText );
// Add each token to the results list.
while ( tokenizer.hasMoreTokens() )
{
result.add( tokenizer.nextToken() );
}
// Return tokenizer list of words.
return result;
}
/** Static initializer. */
static
{
pennPatterns.add( new PatternReplacer( "``", "`` " ) );
pennPatterns.add( new PatternReplacer( "''", " ''" ) );
pennPatterns.add( new PatternReplacer( "([?!\".,;:@#$%&])", " $1 " ) );
pennPatterns.add( new PatternReplacer( "\\.\\.\\.", " ... " ) );
pennPatterns.add( new PatternReplacer( "\\s+", " " ) );
pennPatterns.add( new PatternReplacer( ",([^0-9])", " , $1" ) );
pennPatterns.add( new PatternReplacer( "([^.])([.])([\\])}>\"']*)\\s*$", "$1 $2$3 " ) );
pennPatterns.add( new PatternReplacer( "([\\[\\](){}<>])", " $1 " ) );
pennPatterns.add( new PatternReplacer( "--", " -- " ) );
pennPatterns.add( new PatternReplacer( "$", " " ) );
pennPatterns.add( new PatternReplacer( "^", " " ) );
pennPatterns.add( new PatternReplacer( "([^'])' ", "$1 ' " ) );
pennPatterns.add( new PatternReplacer( "'([sSmMdD]) ", " '$1 " ) );
pennPatterns.add( new PatternReplacer( "'ll ", " 'll " ) );
pennPatterns.add( new PatternReplacer( "'re ", " 're " ) );
pennPatterns.add( new PatternReplacer( "'ve ", " 've " ) );
pennPatterns.add( new PatternReplacer( "'em ", " 'em " ) );
pennPatterns.add( new PatternReplacer( "n't ", " n't " ) );
pennPatterns.add( new PatternReplacer( "'LL ", " 'LL " ) );
pennPatterns.add( new PatternReplacer( "'RE ", " 'RE " ) );
pennPatterns.add( new PatternReplacer( "'EM ", " 'EM " ) );
pennPatterns.add( new PatternReplacer( "'VE ", " 'VE " ) );
pennPatterns.add( new PatternReplacer( "N'T ", " N'T " ) );
pennPatterns.add( new PatternReplacer( " ([Cc])annot ", " $1an not " ) );
pennPatterns.add( new PatternReplacer( " ([Dd])'ye ", " $1' ye " ) );
pennPatterns.add( new PatternReplacer( " ([Gg])imme ", " $1im me " ) );
pennPatterns.add( new PatternReplacer( " ([Gg])onna ", " $1on na " ) );
pennPatterns.add( new PatternReplacer( " ([Gg])otta ", " $1ot ta " ) );
pennPatterns.add( new PatternReplacer( " ([Ll])emme ", " $1em me " ) );
pennPatterns.add( new PatternReplacer( " ([Mm])ore'n ", " $1ore 'n " ) );
pennPatterns.add( new PatternReplacer( " '([Tt])is ", " '$1 is " ) );
pennPatterns.add( new PatternReplacer( " '([Tt])was ", " '$1 was " ) );
pennPatterns.add( new PatternReplacer( " ([Ww])anna ", " $1an na " ) );
pennPatterns.add( new PatternReplacer( " ([Ww])anna ", " $1an na " ) );
pennPatterns.add( new PatternReplacer( " ([Ww])haddya ", " $1ha dd ya " ) );
pennPatterns.add( new PatternReplacer( " ([Ww])hatcha ", " $1ha t cha " ) );
pennPatterns.add( new PatternReplacer( "([A-MO-Za-mo-z])'([tT])" , "$1 '$2" ) );
pennPatterns.add( new PatternReplacer( " ([A-Z]) \\.", " $1. " ) );
pennPatterns.add( new PatternReplacer( "\\s+", " " ) );
pennPatterns.add( new PatternReplacer( "^\\s+", "" ) );
}
}
/*
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Northwestern University
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notice, this list of conditions and the following disclaimers.
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