A .NET Client for REST Interface to Virtuoso

For my current project, I’ve been doing a lot of work related to the Semantic Web.  This has meant figuring out how to write SPARQL queries in order to retrieve data we can use for testing our application.  After figuring out how to do this manually (we used this SPARQL endpoint provided by OpenLink Software), it was time to automate the process.  The Virtuoso product has a REST service interface, but the only example I found here for interacting with it used curl.  Fortunately, some googling revealed a really nice resource in the Yahoo Developer Network with some great examples.

I’ve put together a small solution in Visual Studio 2008 with a console application (VirtuosoPost) which executes queries against http://dbpedia.org/fct/ and returns the query results as XML.  It’s definitely not fancy, but it works.  There’s plenty of room for improvement, and I’ll make updates available here.  The solution does include all the source, so any of you out there who are interested in taking the code in an entirely different direction are welcome to do so.

Adventures in SPARQL

If this blog post seems different than usual, it’s because I’m actually using it to get tech support via Twitter for an issue I’m having.  One of my tasks for my current project has me generating data for use in a test database. DBPedia is the data source, and I’ve been running SPARQL queries to retrieve RDF/XML-formatted data against their Virtuoso endpoint.  For some reason though, the resulting data doesn’t validate.

For example, the following query:

PREFIX owl: <http://www.w3.org/2002/07/owl#>
PREFIX xsd: <http://www.w3.org/2001/XMLSchema#>
PREFIX rdfs: <http://www.w3.org/2000/01/rdf-schema#>
PREFIX rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#>
PREFIX foaf: <http://xmlns.com/foaf/0.1/>
PREFIX dc: <http://purl.org/dc/elements/1.1/>
PREFIX : <http://dbpedia.org/resource/>
PREFIX dbpedia2: <http://dbpedia.org/property/>
PREFIX dbpedia: <http://dbpedia.org/>
PREFIX skos: <http://www.w3.org/2004/02/skos/core#>
SELECT ?property ?hasValue ?isValueOf
{ <http://dbpedia.org/resource/Bank> ?property ?hasValue FILTER (LANG(?hasValue) = ‘en’) .}
{ ?isValueOf ?property <http://dbpedia.org/resource/Bank> }

generates the RDF/XML output here.  If I try to parse the file with an RDF validator (like this one, for example), validation fails.  Removing the attributes from the output takes care of the validation issues, but what I’m not sure of is why the node ids are added in the first place.