How do I consume a sparql endpoint - such as DBPedia in an iphone app

Question

I am looking for tutorials on how to consume and parse data from a sparql endpoint such as DBPedia. I am new to semantic web and rdf and sparql. Would I just treat the response as XML and use one of the many third party xml parsers to read rdf input?

A link to a good tutorial for consuming sparql endpoints on the iphone would be great

Answer 1

You send the query as a HTTP GET request, and parse the result (usually XML or JSON, you can request either) using an XML or JSON parser.

For example the query:

http://dbpedia.org/sparql?query=SELECT+DISTINCT+?concept+WHERE+{+?s+a+?concept+}+LIMIT+50

Will run the SPARQL query:

SELECT DISTINCT ?concept
WHERE {
    ?s a ?concept .
} LIMIT 50

And return the results in XML.

You can test this in curl with:

$ curl -g 'http://dbpedia.org/sparql?query=SELECT+DISTINCT+?concept+WHERE+{+?s+a+?concept+}+LIMIT+50'

If you set the Accept: header you can control the return type, e.g. in curl:

$ curl -g -H 'Accept: application/json' 'http://dbpedia.org/sparql?query=SELECT+DISTINCT+?concept+WHERE+{+?s+a+?concept+}+LIMIT+50'