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https://issues.apache.org/jira/browse/JENA-1556?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16513774#comment-16513774
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ASF GitHub Bot commented on JENA-1556:
--------------------------------------

Github user kinow commented on a diff in the pull request:

    https://github.com/apache/jena/pull/436#discussion_r195658758
  
    --- Diff: 
jena-text/src/main/java/org/apache/jena/query/text/TextIndexLucene.java ---
    @@ -316,6 +326,13 @@ protected Document doc(Entity entity) {
                         if (this.isMultilingual) {
                             // add a field that uses a language-specific 
analyzer via MultilingualAnalyzer
                             doc.add(new Field(e.getKey() + "_" + lang, 
(String) e.getValue(), ftText));
    +                        // add fields for any defined auxiliary indexes
    +                        List<String> auxIndexes = Util.getAuxIndexes(lang);
    +                        if (auxIndexes != null) {
    --- End diff --
    
    Never null I believe. We return an empty list when `lang` is empty. And use 
a `Hashtable` to keep data. But happy to leave it if you prefer to double-check 
it anyway (wonder if we should consider `@Nullable` et `@NotNull` in method 
signatures some day)


> text:query multilingual enhancements
> ------------------------------------
>
>                 Key: JENA-1556
>                 URL: https://issues.apache.org/jira/browse/JENA-1556
>             Project: Apache Jena
>          Issue Type: New Feature
>          Components: Text
>    Affects Versions: Jena 3.7.0
>            Reporter: Code Ferret
>            Assignee: Code Ferret
>            Priority: Major
>              Labels: pull-request-available
>
> This issue proposes two related enhancements of Jena Text. These enhancements 
> have been implemented and a PR can be issued. 
> There are two multilingual search situations that we want to support:
>  # We want to be able to search in one encoding and retrieve results that may 
> have been entered in other encodings. For example, searching via Simplified 
> Chinese (Hans) and retrieving results that may have been entered in 
> Traditional Chinese (Hant) or Pinyin. This will simplify applications by 
> permitting encoding independent retrieval without additional layers of 
> transcoding and so on. It's all done under the covers in Lucene.
>  # We want to search with queries entered in a lossy, e.g., phonetic, 
> encoding and retrieve results entered with accurate encoding. For example, 
> searching vis Pinyin without diacritics and retrieving all possible Hans and 
> Hant triples.
> The first situation arises when entering triples that include languages with 
> multiple encodings that for various reasons are not normalized to a single 
> encoding. In this situation we want to be able to retrieve appropriate result 
> sets without regard for the encodings used at the time that the triples were 
> inserted into the dataset.
> There are several such languages of interest in our application: Chinese, 
> Tibetan, Sanskrit, Japanese and Korean. There are various Romanizations and 
> ideographic variants.
> Encodings may not normalized when inserting triples for a variety of reasons. 
> A principle one is that the {{rdf:langString}} object often must be entered 
> in the same encoding that it occurs in some physical text that is being 
> catalogued. Another is that metadata may be imported from sources that use 
> different encoding conventions and we want to preserve that form.
> The second situation arises as we want to provide simple support for phonetic 
> or other forms of lossy search at the time that triples are indexed directly 
> in the Lucene system.
> To handle the first situation we introduce a {{text}} assembler predicate, 
> {{text:searchFor}}, that specifies a list of language tags that provides a 
> list of language variants that should be searched whenever a query string of 
> a given encoding (language tag) is used. For example, the following 
> {{text:TextIndexLucene/text:defineAnalyzers}} fragment :
> {code:java}
>         [ text:addLang "bo" ; 
>           text:searchFor ( "bo" "bo-x-ewts" "bo-alalc97" ) ;
>           text:analyzer [ 
>             a text:GenericAnalyzer ;
>             text:class "io.bdrc.lucene.bo.TibetanAnalyzer" ;
>             text:params (
>                 [ text:paramName "segmentInWords" ;
>                   text:paramValue false ]
>                 [ text:paramName "lemmatize" ;
>                   text:paramValue true ]
>                 [ text:paramName "filterChars" ;
>                   text:paramValue false ]
>                 [ text:paramName "inputMode" ;
>                   text:paramValue "unicode" ]
>                 [ text:paramName "stopFilename" ;
>                   text:paramValue "" ]
>                 )
>             ] ; 
>           ]
> {code}
> indicates that when using a search string such as "རྡོ་རྗེ་སྙིང་"@bo the 
> Lucene index should also be searched for matches tagged as {{bo-x-ewts}} and 
> {{bo-alalc97}}.
> This is made possible by a Tibetan {{Analyzer}} that tokenizes strings in all 
> three encodings into Tibetan Unicode. This is feasible since the 
> {{bo-x-ewts}} and {{bo-alalc97}} encodings are one-to-one with Unicode 
> Tibetan. Since all fields with these language tags will have a common set of 
> indexed terms, i.e., Tibetan Unicode, it suffices to arrange for the query 
> analyzer to have access to the language tag for the query string along with 
> the various fields that need to be considered.
> Supposing that the query is:
> {code:java}
>     (?s ?sc ?lit) text:query ("rje"@bo-x-ewts) 
> {code}
> Then the query formed in {{TextIndexLucene}} will be:
> {code:java}
>     label_bo:rje label_bo-x-ewts:rje label_bo-alalc97:rje
> {code}
> which is translated using a suitable {{Analyzer}}, 
> {{QueryMultilingualAnalyzer}}, via Lucene's {{QueryParser}} to:
> {code:java}
>     +(label_bo:རྗེ label_bo-x-ewts:རྗེ label_bo-alalc97:རྗེ)
> {code}
> which reflects the underlying Tibetan Unicode term encoding. During 
> {{IndexSearcher.search}} all documents with one of the three fields in the 
> index for term, "རྗེ", will be returned even though the value in the fields 
> {{label_bo-x-ewts}} and {{label_bo-alalc97}} for the returned documents will 
> be the original value "rje".
> This support simplifies applications by permitting encoding independent 
> retrieval without additional layers of transcoding and so on. It's all done 
> under the covers in Lucene.
> Solving the second situation will simplify applications by adding appropriate 
> fields and indexing via configuration in the 
> {{text:TextIndexLucene/text:defineAnalyzers}}. For example, the following 
> fragment
> {code:java}
>         [ text:addLang "zh-hans" ; 
>           text:searchFor ( "zh-hans" "zh-hant" ) ;
>           text:auxIndex ( "zh-aux-han2pinyin" ) ;
>           text:analyzer [
>             a text:DefinedAnalyzer ;
>             text:useAnalyzer :hanzAnalyzer ] ; 
>           ]
>         [ text:addLang "zh-hant" ; 
>           text:searchFor ( "zh-hans" "zh-hant" ) ;
>           text:auxIndex ( "zh-aux-han2pinyin" ) ;
>           text:analyzer [
>             a text:DefinedAnalyzer ;
>             text:useAnalyzer :hanzAnalyzer ] ; 
>           ]
>         [ text:addLang "zh-latn-pinyin" ;
>           text:searchFor ( "zh-latn-pinyin" "zh-aux-han2pinyin" ) ;
>           text:analyzer [
>             a text:DefinedAnalyzer ;
>             text:useAnalyzer :pinyin ] ; 
>           ]        
>         [ text:addLang "zh-aux-han2pinyin" ;
>           text:searchFor ( "zh-latn-pinyin" "zh-aux-han2pinyin" ) ;
>           text:analyzer [
>             a text:DefinedAnalyzer ;
>             text:useAnalyzer :pinyin ] ; 
>           text:indexAnalyzer :han2pinyin ; 
>           ]
> {code}
> defines language tags for Traditional, Simplified, Pinyin and an _auxiliary_ 
> tag {{zh-aux-han2pinyin}} associated with an {{Analyzer}}, {{:han2pinyin}}. 
> The purpose of the auxiliary tag is to define an {{Analyzer}} that will be 
> used during indexing and to specify a list of tags that should be searched 
> when the auxiliary tag is used with a query string. 
> Searching is then done via multi-encoding support discussed above. In this 
> example the {{Analyzer}}, {{:han2pinyin}}, tokenizes strings in {{zh-hans}} 
> and {{zh-hant}} as the corresponding pinyin so that at search time a pinyin 
> query will retrieve appropriate triples inserted in Traditional or Simplified 
> Chinese. Such a query would appear as:
> {code}
>     (?s ?sc ?lit ?g) text:query ("jīng"@zh-aux-han2pinyin)
> {code}
> The auxiliary field support is needed to accommodate situations such as 
> pinyin or sound-ex which are not exact, i.e., one-to-many rather than 
> one-to-one as in the case of Simplified and Traditional.
> {{TextIndexLucene}} adds a field for each of the auxiliary tags associated 
> with the tag of the triple object being indexed. These fields are in addition 
> to the un-tagged field and the field tagged with the language of the triple 
> object literal.



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