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From "Mark Miller (JIRA)" <>
Subject [jira] Commented: (LUCENE-1029) Illegal character replacements in ISOLatin1AccentFilter
Date Mon, 15 Oct 2007 11:58:50 GMT


Mark Miller commented on LUCENE-1029:

> With the accent filter, running the Swedish word "kön" through the filter would create
"kon". The first means "gender" and the second "cow". That would not be accetable.

I am feeling lazy right now, but it seems to me you could find a similar rare stemming example
(eg something that means something else in its stemmed form). The process is algorithmic after
all, and there are many language with plenty of words out there.

Regardless, it doesn't seem this filter claims it will maintain the meaning of "kön"...rather
it will strip the '..' off the top of the 'o'. Its a brute force and somewhat dangerous filter
from the get go...stripping accents its not a valid language operation that I know of.

I'll leave at that from my side of the argument <g> Let the Lucene gods speak.

> Illegal character replacements in ISOLatin1AccentFilter
> -------------------------------------------------------
>                 Key: LUCENE-1029
>                 URL:
>             Project: Lucene - Java
>          Issue Type: Bug
>          Components: Analysis
>    Affects Versions: 2.2
>            Reporter: Marko Asplund
> The ISOLatin1AccentFilter class is responsible for replacing "accented characters in
the ISO Latin 1 character set by their unaccented equivalent".
> Some of the replacements performed for scandinavian characters (used e.g. in the finnish,
swedish, danish languages etc.) are illegal. The scandinavian characters are different from
the accented characters used e.g. in latin based languages such as french in that these characters
(ä, ö, å) represent entirely independent sounds in the language and therefore cannot be
represented with any other sound without change of meaning. It is therefore illegal to replace
these characters with any other character.
> This means for example that you can't change the finnish word sää (weather) to saa
(will have) because these are two entirely different words with different meaning. The same
applies to scandinavian languages as well.
> There's no connection between the sounds represented by ä and a; ö and o or å and
> In addition to the three characters mentioned above danish and norwegian use other special
characters such as ø and æ. It should be checked if the replacement is legal for these characters.

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