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Date: Mon, 8 Nov 2010 15:09:06 -0500 (EST)
From: "Steven Rowe (JIRA)" <jira@apache.org>
To: dev@lucene.apache.org
Subject: [jira] Created: (LUCENE-2747) Deprecate/remove language-specific
 tokenizers in favor of StandardTokenizer
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Deprecate/remove language-specific tokenizers in favor of StandardTokenizer
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                 Key: LUCENE-2747
                 URL: https://issues.apache.org/jira/browse/LUCENE-2747
             Project: Lucene - Java
          Issue Type: Improvement
          Components: Analysis
    Affects Versions: 3.1, 4.0
            Reporter: Steven Rowe
             Fix For: 3.1, 4.0


As of Lucene 3.1, StandardTokenizer implements UAX#29 word boundary rules to provide language-neutral tokenization.  Lucene contains several language-specific tokenizers that should be replaced by UAX#29-based StandardTokenizer (deprecated in 3.1 and removed in 4.0).  The language-specific *analyzers*, by contrast, should remain, because they contain language-specific post-tokenization filters.  The language-specific analyzers should switch to StandardTokenizer in 3.1.

Some usages of language-specific tokenizers will need additional work beyond just replacing the tokenizer in the language-specific analyzer.  

For example, PersianAnalyzer currently uses ArabicLetterTokenizer, and depends on the fact that this tokenizer breaks tokens on the ZWNJ character (zero-width non-joiner; U+200C), but in the UAX#29 word boundary rules, ZWNJ is not a word boundary.  Robert Muir has suggested using a char filter converting ZWNJ to spaces prior to StandardTokenizer in the converted PersianAnalyzer.

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