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https://issues.apache.org/jira/browse/JENA-1313?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15959219#comment-15959219
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Andy Seaborne commented on JENA-1313:
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The argument to {{ORDER BY}} is a function that returns a value used by the
internal comparator, not a function that is a comparator returns in -1,0,1.
I don't see how the single {{?value}} above works - comparators need two values
from the data.
We could tunnel a comparator through as in
{{collate:compare(<java:MyComparator>, 'fi'))}} where {{<java:MyComparator>}}
is a two argument function, called NlogN times with two data values.
It is tunnelling through SPARQL syntax, not strict SPARQL evaluation. It isn't
sorting the value of evaluating {{(<java:MyComparator>, ?value)}} based on the
"compare" usage.
To go forward, could we implement a {{collate:collate(?v, 'fi')}} function that
returns sort keys that then can be sorted as currently, maybe a fast path. Not
worry to much about efficiency in a first pass, get something going and then
see if efficiency is actually an issue or not because it should be that
efficiency is to do with the implementation of {{collate:collate}}, not the
user usage. Hopefully.
> 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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