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From "Robert Muir (JIRA)" <j...@apache.org>
Subject [jira] Updated: (LUCENE-1488) issues with standardanalyzer on multilingual text
Date Sat, 13 Jun 2009 04:01:07 GMT

     [ https://issues.apache.org/jira/browse/LUCENE-1488?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Robert Muir updated LUCENE-1488:
--------------------------------

    Attachment: LUCENE-1488.txt

just an update, still more work to be done.

some of the components are javadoc'ed and have pretty good tests (case folding and normalization).
These might be useful to someone in the meantime.

also added some tests to TestICUAnalyzer for various jira issues (LUCENE-1032, LUCENE-1215,
LUCENE-1343, LUCENE-1545, etc) that are solved here. 


> issues with standardanalyzer on multilingual text
> -------------------------------------------------
>
>                 Key: LUCENE-1488
>                 URL: https://issues.apache.org/jira/browse/LUCENE-1488
>             Project: Lucene - Java
>          Issue Type: Wish
>          Components: contrib/analyzers
>            Reporter: Robert Muir
>            Priority: Minor
>         Attachments: ICUAnalyzer.patch, LUCENE-1488.patch, LUCENE-1488.txt
>
>
> The standard analyzer in lucene is not exactly unicode-friendly with regards to breaking
text into words, especially with respect to non-alphabetic scripts.  This is because it is
unaware of unicode bounds properties.
> I actually couldn't figure out how the Thai analyzer could possibly be working until
i looked at the jflex rules and saw that codepoint range for most of the Thai block was added
to the alphanum specification. defining the exact codepoint ranges like this for every language
could help with the problem but you'd basically be reimplementing the bounds properties already
stated in the unicode standard. 
> in general it looks like this kind of behavior is bad in lucene for even latin, for instance,
the analyzer will break words around accent marks in decomposed form. While most latin letter
+ accent combinations have composed forms in unicode, some do not. (this is also an issue
for asciifoldingfilter i suppose). 
> I've got a partially tested standardanalyzer that uses icu Rule-based BreakIterator instead
of jflex. Using this method you can define word boundaries according to the unicode bounds
properties. After getting it into some good shape i'd be happy to contribute it for contrib
but I wonder if theres a better solution so that out of box lucene will be more friendly to
non-ASCII text. Unfortunately it seems jflex does not support use of these properties such
as [\p{Word_Break = Extend}] so this is probably the major barrier.
> Thanks,
> Robert

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