EnglishTokeniser (Terrier Information Retrieval Platform 5.5 API)

java.lang.Object
- org.terrier.indexing.tokenisation.Tokeniser
- - org.terrier.indexing.tokenisation.EnglishTokeniser

All Implemented Interfaces:

java.io.Serializable
```
public class EnglishTokeniser
extends Tokeniser
```
Tokenises text obtained from a text stream assuming English language. Acceptable characters are A-Z a-z and 0-9. All other characters cause a new token.
Furthermore, there is an additional checking of terms, to reduce index noise, as follows:
1. Any term which is longer than max.term.length (usually 20 characters) is discarded.
2. Any term which has more than 4 digits is discarded.
3. Any term which has more than 3 consecutive identical characters are discarded.
Properties:
- lowercase - should all terms be lowercased or not?
- max.term.length - maximum acceptable term length, default is 20.
Author:

Gianni Amati, Ben He, Vassilis Plachouras, Craig Macdonald

See Also:

Serialized Form

Field Summary

Fields
Modifier and Type	Field	Description
`protected static boolean`	`DROP_LONG_TOKENS`	Whether tokens longer than MAX_TERM_LENGTH should be dropped.
`protected static int`	`maxNumOfDigitsPerTerm`	The maximum number of digits that are allowed in valid terms.
`protected static int`	`maxNumOfSameConseqLettersPerTerm`	The maximum number of consecutive same letters or digits that are allowed in valid terms.

Fields inherited from class org.terrier.indexing.tokenisation.Tokeniser
EMPTY_STREAM

Constructor Summary

Constructors
Constructor Description

EnglishTokeniser()

Method Summary

All Methods Instance Methods Concrete Methods
Modifier and Type Method Description

TokenStream tokenise(java.io.Reader reader)
Tokenises the text obtained from the specified reader.
- Methods inherited from class org.terrier.indexing.tokenisation.Tokeniser
  getTokeniser, getTokens, getTokens
- Methods inherited from class java.lang.Object
  clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

- Field Detail
  - maxNumOfDigitsPerTerm
```
protected static final int maxNumOfDigitsPerTerm
```
    The maximum number of digits that are allowed in valid terms.
    
    See Also:
    
    Constant Field Values
  - maxNumOfSameConseqLettersPerTerm
```
protected static final int maxNumOfSameConseqLettersPerTerm
```
    The maximum number of consecutive same letters or digits that are allowed in valid terms.
    
    See Also:
    
    Constant Field Values
  - DROP_LONG_TOKENS
```
protected static final boolean DROP_LONG_TOKENS
```
    Whether tokens longer than MAX_TERM_LENGTH should be dropped.
    
    See Also:
    
    Constant Field Values
- Constructor Detail
  - EnglishTokeniser
```
public EnglishTokeniser()
```
- Method Detail
  - tokenise
```
public TokenStream tokenise(java.io.Reader reader)
```
    Description copied from class: Tokeniser
    
    Tokenises the text obtained from the specified reader.
    
    Specified by:
    
    tokenise in class Tokeniser
    
    Parameters:
    
    reader - Stream of text to be tokenised
    
    Returns:
    
    a TokenStream of the tokens found in the text.