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https://issues.apache.org/jira/browse/JENA-1313?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15953502#comment-15953502
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Osma Suominen commented on JENA-1313:
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{quote}
I have no idea how collate:collate(?value, ?lang) would work except it is
almost certain to have instability problems comparing across languages in a
single sort. See my example in the message of Oct 25, 2016. Java "sort" can
throw an exception because the comparator contract is broken.
{quote}
My perhaps naive inclination would be to implement this function like this:
1. Create a Collator using the supplied {{?lang}} as the locale
2. Using the Collator, convert the {{?value}} to a byte string
Even when called several times with different {{?lang}} parameters, this should
still be deterministic and produce a set of byte strings that can be compared.
Now the order between byte strings generated using different {{?lang}} values
may not make sense to a human, but it should still be consistent, since in the
end we are comparing the byte strings and they are conceptually just large
numbers which have a well-defined order. So no contracts should be broken nor
exceptions thrown.
By the way, the parameters could just as well be swapped, i.e.
{{collate:collate(?lang, ?value)}}, to make it more explicit that the language
is more "fundamental" here.
> Language-specific collation in ARQ
> ----------------------------------
>
> Key: JENA-1313
> URL: https://issues.apache.org/jira/browse/JENA-1313
> Project: Apache Jena
> Issue Type: Improvement
> Components: ARQ
> Affects Versions: Jena 3.2.0
> Reporter: Osma Suominen
>
> As [discussed|http://markmail.org/message/v2bvsnsza5ksl2cv] on the users
> mailing list in October 2016, I would like to change ARQ collation of literal
> values to be language-aware and respect language-specific collation rules.
> This would probably involve changing at least the
> [NodeUtils.compareLiteralsBySyntax|https://github.com/apache/jena/blob/master/jena-arq/src/main/java/org/apache/jena/sparql/util/NodeUtils.java#L199]
> method.
> It currently sorts by lexical value first, then by language tag. Since the
> collation order needs to be stable across all possible literal values, I
> think the safest way would be to sort by language tag first, then by lexical
> value according to the collation rules for that language.
> But what about subtags like {{@en-US}} or {{@pt-BR}}? Can they have different
> collation rules than the main language? It would be a bit strange if all
> {{@en-US}} literals sorted after {{@en}} literals...
> It would be good to check how Dydra does this and possibly take the same
> approach. See the message linked above for further backgound.
> I've been talking with [~kinow] about this and he may be interested in
> implementing it.
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