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From "Robert Muir (JIRA)" <j...@apache.org>
Subject [jira] Commented: (LUCENE-2067) Czech Stemmer
Date Sat, 28 Nov 2009 20:19:20 GMT

    [ https://issues.apache.org/jira/browse/LUCENE-2067?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12783276#action_12783276
] 

Robert Muir commented on LUCENE-2067:
-------------------------------------

Hi Simon, I think you are referring to the 2007 paper: http://clef-campaign.org/2007/working_notes/DolamicCLEF2007.pdf,
which is very similar.

The 2009 paper (referenced by the code, but you need ACM account to get it), http://portal.acm.org/citation.cfm?id=1598600
describes this in pseudocode as:

{noformat}
if (word ends with "e*") then replace by "*" return;
{noformat}

Sorry for the confusion (pointing you at a slightly different algorithm)... 

btw here is a description of what this rule does from http://www.seelrc.org/projects/casebooks/appendixcz.pdf

Many words in Czech have what we call mobile e. This is an e that appears (usually
before the last consonant in the stem) when there is no ending after the stem, but is absent
when there is a case ending. 
Here are some examples: 
* pes 'dog' Nsg : psi 'dogs' Npl
* otec 'father' Nsg : otce 'father' Gsg
* deska 'board' Nsg : desek 'boards' Gpl.

bq. I also see no reason why the CzechStemFilter should be none final.
I will make the stemfilter final, thanks!

> Czech Stemmer
> -------------
>
>                 Key: LUCENE-2067
>                 URL: https://issues.apache.org/jira/browse/LUCENE-2067
>             Project: Lucene - Java
>          Issue Type: New Feature
>          Components: contrib/analyzers
>            Reporter: Robert Muir
>            Assignee: Robert Muir
>            Priority: Minor
>             Fix For: 3.1
>
>         Attachments: LUCENE-2067.patch, LUCENE-2067.patch, LUCENE-2067.patch
>
>
> Currently, the CzechAnalyzer is merely stopwords, and there isn't a czech stemmer in
snowball.
> This patch implements the light stemming algorithm described in: http://portal.acm.org/citation.cfm?id=1598600
> In their measurements, it improves MAP 42%
> The analyzer does not use this stemmer if LUCENE_VERSION <= 3.0, for back compat.

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