Tomoko Uchida created LUCENE-7273:
-------------------------------------
Summary: New kuromoji TokenFilter to keep tokens by part-of-speech
tags
Key: LUCENE-7273
URL: https://issues.apache.org/jira/browse/LUCENE-7273
Project: Lucene - Core
Issue Type: Improvement
Components: modules/analysis
Reporter: Tomoko Uchida
Priority: Minor
Kuromoji has JapanesePartOfSpeechStopFilter to drop tokens by their
part-of-speech tags. In some cases, it would be convenient to keep tokens
according to "keep" POS tags list.
Example usage:
{code:java}
// keeps proper nouns - location names only
String[] tags = new String[]{"名詞-固有名詞-地域-一般"};
Set<String> keeptags = new HashSet<>();
for (String tag: tags) {
keeptags.add(tag);
}
JapaneseTokenizer tokenizer = new JapaneseTokenizer(null, false,
JapaneseTokenizer.Mode.SEARCH);
JapanesePartOfSpeechKeepFilter stream = new
JapanesePartOfSpeechKeepFilter(tokenizer, keeptags);
{code}
{code:xml}
<!-- (Solr) analyzer definition -->
<fieldType name="text_ja_propernoun" class="solr.TextField"
positionIncrementGap="100"
autoGeneratePhraseQueries="false">
<analyzer>
<tokenizer class="solr.JapaneseTokenizerFactory" mode="normal"/>
<filter class="solr.CJKWidthFilterFactory"/>
<filter class="solr.JapanesePartOfSpeechKeepFilterFactory"
tags="lang/keeptags_ja.txt" />
<filter class="solr.JapaneseKatakanaStemFilterFactory"
minimumLength="4"/>
<filter class="solr.LowerCaseFilterFactory"/>
</analyzer>
</fieldType>
{code}
Of course it can be achieved by using JapanesePartOfSpeechStopFilter, however
because there are about 70 part-of-speeches, it can be cumbersome to list all
stop tags to keep tokens with few POS tags of interest.
I'll add a patch soon.
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