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https://issues.apache.org/jira/browse/LUCENE-1488?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12802596#action_12802596
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Robert Muir commented on LUCENE-1488:
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Thanks for sharing those results! Yes the bigram behavior (right now enabled
for Han, Lao, Khmer, and Myanmar) is an attempt to boost relevance in a
consistent way since we do not have dictionary-based word segmentation for
those writing systems, only the ability to segment into syllables.
In the next patch I'll make it easier to configure this behavior, and turn it
off when you want, without writing your own analyzer.
I am glad to hear the syllable segmentation algorithm is working well!
The credit really belongs to the Pan Localization Project, I simply implemented
the algorithm described here:
http://www.panl10n.net/english/final%20reports/pdf%20files/Laos/LAO06.pdf
You can see the code in Lao.rbbi in the patch, warning, as it mentions, I am
pretty sure Lao numeric digits are not yet working correctly, but hopefully I
will fix those too in the next version.
> multilingual analyzer based on icu
> ----------------------------------
>
> Key: LUCENE-1488
> URL: https://issues.apache.org/jira/browse/LUCENE-1488
> Project: Lucene - Java
> Issue Type: New Feature
> Components: contrib/analyzers
> Reporter: Robert Muir
> Assignee: Robert Muir
> Priority: Minor
> Fix For: 3.1
>
> Attachments: ICUAnalyzer.patch, LUCENE-1488.patch, LUCENE-1488.patch,
> LUCENE-1488.patch, LUCENE-1488.txt, 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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