LinqToRdf - SPARQL Query Generation

Progress with the LINQ to RDF Query Provider is continuing apace. I have been pretty tightly focused for the last few days, so I haven’t ad time to post an update. I’ve lately been working on a SPARQL query, which will allow me a much richer palette to play with. Here’s the current version of the LINQ query I’m using to test the RdfSparqlQuery class.

[<span style="color:rgb(0,128,128);">TestMethod</span>]
<span style="color:rgb(0,0,255);">public</span> <span style="color:rgb(0,0,255);">void</span> SparqlQuery()
    <span style="color:rgb(0,0,255);">string</span> urlToRemoteSparqlEndpoint = <span style="color:rgb(128,0,0);">@<a href="http://someUri">http://someUri</a></span>;
    <span style="color:rgb(0,128,128);">TripleStore</span> ts = <span style="color:rgb(0,0,255);">new</span> <span style="color:rgb(0,128,128);">TripleStore</span>();
    ts.EndpointUri = urlToRemoteSparqlEndpoint;
    ts.QueryType = <span style="color:rgb(0,128,128);">QueryType</span>.RemoteSparqlStore;
    <span style="color:rgb(0,128,128);">IRdfQuery</span><<span style="color:rgb(0,128,128);">Track</span>> qry = <span style="color:rgb(0,0,255);">new</span> <span style="color:rgb(0,128,128);">RDF</span>(ts).ForType<<span style="color:rgb(0,128,128);">Track</span>>();
    var q = from t <span style="color:rgb(0,0,255);">in</span> qry
        where t.Year == 2006 &&
        t.GenreName == <span style="color:rgb(128,0,0);">"History 5 | Fall 2006 | UC Berkeley"</span>
        select <span style="color:rgb(0,0,255);">new</span> {t.Title, t.FileLocation};
    <span style="color:rgb(0,0,255);">foreach</span>(var track <span style="color:rgb(0,0,255);">in</span> q){
        <span style="color:rgb(0,128,128);">Trace</span>.WriteLine(track.Title + <span style="color:rgb(128,0,0);">": "</span> + track.FileLocation);

And here’s what it’s producing as output:

@prefix a: .

SELECT ?Title, ?FileLocation
?Track ?Title .
?Track ?ArtistName .
?Track ?AlbumName .
?Track ?Year .
?Track ?GenreName .
?Track ?Comment .
?Track ?FileLocation .
?Track ?Rating .
((t.Year)=(2006^^xsdt:int))&&((t.GenreName)=(“History 5 | Fall 2006 | UC Berkeley”^^xsdt:string))

as you can see, the query is fairly close. I just have to:

  • Convert the property names in the filters to use the free variable name chosen for the object of a property assertion.

  • Restrict the variables enumerated in the graph definition to just those required for the projection (if there is a projection)

  • Use the UNION operator to allow disjunctions (OrElse expression types)

  • Add the XSDT (XML Schema Datatypes) namespace to the prefixes

  • Use standard SPARQL variable syntax for the ?Track

I also need to find a _fast _back-end SPARQL enabled triple store that I can start to run these queries against. A month or two ago I did a .NET conversion of Jena using IKVM. I may end up going back to that. Any other suggestions would be welcome.

If you want to have a play with it, or take a look at how to produce a LINQ Query provider, then you can use Subversion to get the code from Google. Use the command below:

svn checkout linqtordf

Dialogue & Discussion