Hello,
i am trying to use Virtuoso as RDF store for a C# application with .Net
4, but i have some issues with the ADO.NET library. I have no troubles
creating triples with SPARQL using SPASQL, but the retrieval is
problematic. In the result set, all typed literals are strings without
type information. I get the IRI as SqlExtendedString and the literals
with language information as SqlRdfBox, so no problem there. Now i am
wondering what i'm doing wrong.
This is how i access the data:
DataTable results = new DataTable();
results.Columns.Add("s", typeof(System.Object));
results.Columns.Add("p",typeof(System.Object));
results.Columns.Add("o", typeof(System.Object));
VirtuosoCommand cmd = Connection.CreateCommand();
cmd.CommandText = "SPARQL select * where {?s ?p ?o.}"; //just an example
here
VirtuosoDataAdapter adapter = new VirtuosoDataAdapter(cmd);
adapter.Fill(results);
I also tried to use the RDF/XML output, although not optimal
performance-wise, it kind of worked. One thing i noticed though, was
that ASK statments produce malformed XML.
As example, this statment
SPARQL define output:format "RDF/XML" ask where {?s ?p ?o.};
produced
<rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#";
xmlns:rs="http://www.w3.org/2005/sparql-results#";
xmlns:xsd="http://www.w3.org/2001/XMLSchema#"; >
<rs:results rdf:nodeID="rset">
<rs:boolean
rdf:datatype="http://www.w3.org/2001/XMLSchema#boolean";>1</rs:boolean>
</results>
</rdf:RDF>
The prefix of the closing result tag is missing. You can try it in the
Interactive SQL form of the conductor.
My system specs:
OS: Windows 7 64-bit
Virtuoso: Open-Source-Edition Version 06.01.3127 - Build Jul 9 2010 32-bit
virtado3.dll: Version 6.2.3128.1
It would be great if somebody could help me to resolve my issues.
Cheers,
Moritz
