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https://issues.apache.org/jira/browse/LUCENE-1488?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12785036#action_12785036
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DM Smith commented on LUCENE-1488:
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Robert, just finished reviewing the code. Looks great! Doesn't look like
there's too much left. All I see is a bit of JavaDoc and an extraneous unused
variable (ICUTokenizer: private PositionIncrementAttribute posIncAtt;)
The documentation in ICUNormalizationFilter is very instructive. Kudos. The
only part that's hard to for me to understand is the filter order dependency,
but then again that's a hard topic in the first place.
I'm wondering whether it would make sense to have multiple representations of a
token with the same position in the index. Specifically, transliterations and
case-folding. That is, the one is a "synonym" for the other. Is that possible
and does it make sense? I'm imagining a use case where a end user enters for a
search request a Latin script transliteration of Greek "uios" but might also
enter "υιος".
The other question on my mind is that given a text of German, Greek and Hebrew
(three distinct scripts) does it make sense to apply stop words to them based
on script? And should stop words be normalized on load with the
ICUNormalizationFilter? Or is it a given that they work as is?
Can/How does all this integrate with stemmers?
Again, many thanks! (Btw, special thanks for this working with 2.9 and Java
1.4!)
> 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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