[SOLVED] Simple SPARQL query of foaf RDF not working

Simple SPARQL query of foaf RDF not working

I'm new at semantic web, where I learn basics, but I'm stuck at the beginning.

After reading this link: http://www.cambridgesemantics.com/semantic-university/sparql-by-example, I try some examples by myself, but without success.

For example, using OpenLink Virtuoso SPARQL Query Editor http://demo.openlinksw.com/sparql, I put at Default Graph URI this http://njh.me/foaf.rdf and simple query

 PREFIX foaf:  <http://xmlns.com/foaf/0.1/>
 select ?name
 where 
 {
 ?person foaf:name ?name .
 }

to get name of a person who is owner of this RDF file. Also, if I put following query

PREFIX foaf:  <http://xmlns.com/foaf/0.1/>
select ?name
where 
{
?OnlineAcount foaf:name ?name .
}

nothing is happening.

Where I make mistake?

The same situation is with https://ai.wu.ac.at/~polleres/foaf.rdf, http://richard.cyganiak.de/foaf.rdf for the first query.

Any help at the beginning of my semantic tour will be appreciated :)

Thanks in advance.

Solution

Below the query input pane, there's an option for Sponging. You need to select the option Retrieve remote RDF data for all missing source graphs. Then you'll get results. However, the file that you mentioned actually has lots of foaf:name triples, not just one for the creator of the file. You might try select ?person ?name to see what else is in that data.