[Virtuoso-devel] usage of datatype in FILTER sometimes fails

[Lorenz Bühmann]

Hi,

starting from this query on the official DBpedia endpoint ( 
http://dbpedia.org/sparql)

PREFIX  rdfs: <http://www.w3.org/2000/01/rdf-schema#>
PREFIX  res: <http://dbpedia.org/resource/>
PREFIX  foaf: <http://xmlns.com/foaf/0.1/>
PREFIX  dbo: <http://dbpedia.org/ontology/>
PREFIX  rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#>

SELECT DISTINCT  ?date
WHERE
  { res:Charmed dbo:starring ?actor .
    ?actor dbo:birthDate ?date
  }

i get some dates back. When i now bind one of these dates by using a 
FILTER which leads to e.g. this query

SELECT *
WHERE
{ <http://dbpedia.org/resource/Charmed> 
<http://dbpedia.org/ontology/starring> ?actor .
    ?actor <http://dbpedia.org/ontology/birthDate> ?date
    FILTER ( ?date = 
"1973-06-15"^^<http://www.w3.org/2001/XMLSchema#date> )
}

the resultset is empty. Is this a bug? As a workaround i could of course 
use

SELECT *
WHERE
{ <http://dbpedia.org/resource/Charmed> 
<http://dbpedia.org/ontology/starring> ?actor .
    ?actor <http://dbpedia.org/ontology/birthDate> ?date
    FILTER ( STR(?date) = "1973-06-15")
}

but the other way should also work.

I checked this also on http://live.dbpedia.org/sparql. Here it is 
interesting that for some values it is working, e.g. running

SELECT *
WHERE
{<http://dbpedia.org/resource/Charmed> 
<http://dbpedia.org/ontology/starring> ?actor .
    ?actor <http://dbpedia.org/ontology/birthDate> ?date
    FILTER ( ?date = 
"1980-05-19"^^<http://www.w3.org/2001/XMLSchema#date> )
}

and for others not, e.g.

SELECT *
WHERE
{<http://dbpedia.org/resource/Charmed> 
<http://dbpedia.org/ontology/starring> ?actor .
    ?actor <http://dbpedia.org/ontology/birthDate> ?date
    FILTER ( ?date = 
"1965-10-01"^^<http://www.w3.org/2001/XMLSchema#date> )
}



Regards,
Lorenz