SPARQL filter language if possible in multiple value context

Question

Consider the following extract from the GeoNames database :

@prefix gn:    <http://www.geonames.org/ontology#> .
@prefix rdfs:  <http://www.w3.org/2000/01/rdf-schema#> .

<http://sws.geonames.org/690791/>
        a                        gn:Feature ;
        gn:featureClass          gn:A ;
        gn:featureCode           gn:A.PCLI ;
        gn:alternateName         "Україна"@uk , "ܐܘܟܪܢܝܐ"@arc ,  "Ուկրաինա"@hy , "ウクライナ"@ja , "Úkraína"@is;
        gn:name                  "Ukraine" ;
        gn:officialName          "Ucraína"@gl , "Ukraine"@fr , "U-crai-na (Ukraine)"@vi , "ཡུ་ཀརེན།"@bo.

So, I'm trying to get the name in a specif language, for example fr and if it's not available fall back to the default. Moreover, this name can come from any of the three predicates: gn:alternateName , gn:name and gn:officialName.

So for example, for this sample, I expect to recover

----------------
| name         |
================
| "Ukraine"@fr |
----------------

But with my current solution :

PREFIX gn:        <http://www.geonames.org/ontology#>
PREFIX rdfs:      <http://www.w3.org/2000/01/rdf-schema#>

SELECT DISTINCT ?name
WHERE {
    values ?nameBearing { gn:name gn:alternateName gn:officialName}
    values ?countryfc { gn:A.PCLI gn:A.PCLD gn:A.PCLIX }
    ?loc    gn:featureCode      ?countryfc;

    OPTIONAL
    {
        ?loc    ?nameBearing        ?nameFR
        FILTER(langMatches(lang(?nameFR), "fr"))
    }

    OPTIONAL
    {
        ?loc    ?nameBearing        ?nameOTHER
        FILTER(langMatches(lang(?nameOTHER), ""))
    }

    BIND(COALESCE(?nameFR, ?nameOTHER) AS ?name)
}

I get

----------------
| name         |
================
| "Ukraine"    |
|              |
| "Ukraine"@fr |
----------------

probably because the way multiple values for a predicate is evaluated in SPARQL.

So is there any way to "group by ?loc" and get only values in one language?

Do you want to know exactly what language it is in or you don't as long as it is either? What I mean is that you have separated `?nameFR` from `?nameOther` and if this is what you want or `?name` would do? — Artemis, Jun 03 '15 at 15:30
No, I don't need to know the language, but I do need to get the French name whenever it's avaliable — gustavo-vm, Jun 03 '15 at 23:15

score 1 · Answer 1 · answered Jun 03 '15 at 16:25

You can start with a query like this that finds name values and partitions them into French names and default (i.e., non-French) names:

prefix gn:    <http://www.geonames.org/ontology#>
prefix rdfs:  <http://www.w3.org/2000/01/rdf-schema#>

select ?s ?name ?frenchName ?defaultName where {
  values ?name { gn:alternateName gn:name gn:officialName }
  ?s ?name ?name_
  bind(if(langMatches(lang(?name_),"fr"),?name_,?undef) as ?frenchName)
  bind(if(langMatches(lang(?name_),"fr"),?undef,?name_) as ?defaultName)
}

--------------------------------------------------------------------------------------------------
| s                                 | name             | frenchName   | defaultName              |
==================================================================================================
| <http://sws.geonames.org/690791/> | gn:alternateName |              | "Úkraína"@is             |
| <http://sws.geonames.org/690791/> | gn:alternateName |              | "ウクライナ"@ja               |
| <http://sws.geonames.org/690791/> | gn:alternateName |              | "Ուկրաինա"@hy            |
| <http://sws.geonames.org/690791/> | gn:alternateName |              | "ܐܘܟܪܢܝܐ"@arc            |
| <http://sws.geonames.org/690791/> | gn:alternateName |              | "Україна"@uk             |
| <http://sws.geonames.org/690791/> | gn:name          |              | "Ukraine"                |
| <http://sws.geonames.org/690791/> | gn:officialName  |              | "ཡུ་ཀརེན།"@bo            |
| <http://sws.geonames.org/690791/> | gn:officialName  |              | "U-crai-na (Ukraine)"@vi |
| <http://sws.geonames.org/690791/> | gn:officialName  | "Ukraine"@fr |                          |
| <http://sws.geonames.org/690791/> | gn:officialName  |              | "Ucraína"@gl             |
--------------------------------------------------------------------------------------------------

That's a start, but sample and coalesce don't seem to work the way we'd want here. E.g., we can't do coalesce(sample(?frenchName),sample(?defaultName)) to get a single name.

…

SPARQL filter language if possible in multiple value context

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