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Date: Mon, 7 Dec 2009 15:31:18 +0000 (UTC)
From: "Robert Muir (JIRA)" <jira@apache.org>
To: java-dev@lucene.apache.org
Subject: [jira] Commented: (LUCENE-1343) A replacement for
 ISOLatin1AccentFilter that does a more thorough job of removing diacritical
 marks or non-spacing modifiers.
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    [ https://issues.apache.org/jira/browse/LUCENE-1343?page=3Dcom.atlassia=
n.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=3D127=
86946#action_12786946 ]=20

Robert Muir commented on LUCENE-1343:
-------------------------------------

bq. Robert Muir, Would it make sense to have a Greek filter that strips dia=
critics? My thought is that if the letter is Greek then the diacritics woul=
d be removed, but otherwise it would not.

The GreekLowerCaseFilter (incorrectly named) does this also, somewhat. it r=
emoves tone marks... but this might not be what you "want" (depending on wh=
at that is), if you are dealing with polytonic Greek (sorry for my ignoranc=
e of the biblical test you are looking at, but I think it is ancient Greek?=
)

bq. Similar question for Hebrew, I see value in two filters: one would stri=
p cantillation and the other, vowel points. Or would it be better to have o=
ne that can do both depending on flags?

This depends on your use case, and then you have dagesh,shin dot, too... Th=
ese are all NSMs. But this is going to depend on the user, and I think ever=
y person will need their own, they can use CharFilter or other ways of defi=
ning these tables.


> A replacement for ISOLatin1AccentFilter that does a more thorough job of =
removing diacritical marks or non-spacing modifiers.
> -------------------------------------------------------------------------=
----------------------------------------------------
>
>                 Key: LUCENE-1343
>                 URL: https://issues.apache.org/jira/browse/LUCENE-1343
>             Project: Lucene - Java
>          Issue Type: Improvement
>          Components: Analysis
>            Reporter: Robert Haschart
>            Priority: Minor
>         Attachments: normalizer.jar, UnicodeCharUtil.java, UnicodeNormali=
zationFilter.java, UnicodeNormalizationFilterFactory.java
>
>
> The ISOLatin1AccentFilter takes Unicode characters that have diacritical =
marks and replaces them with a version of that character with the diacritic=
al mark removed.  For example =C3=A9 becomes e.  However another equally va=
lid way of representing an accented character in Unicode is to have the una=
ccented character followed by a non-spacing modifier character (like this: =
 e=CC=81  )    The ISOLatin1AccentFilter doesn't handle the accents in deco=
mposed unicode characters at all.    Additionally there are some instances =
where a word will contain what looks like an accented character, that is ac=
tually considered to be a separate unaccented character  such as  =C5=81  b=
ut which to make searching easier you want to fold onto the latin1  lookali=
ke  version   L  .  =20
> The UnicodeNormalizationFilter can filter out accents and diacritical mar=
ks whether they occur as composed characters or decomposed characters, it c=
an also handle cases where as described above characters that look like the=
y have diacritics (but don't) are to be folded onto the letter that they lo=
ok like ( =C5=81  -> L )

--=20
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