SPARQL for DBPedia: Undefined namespace prefix at 'dbpedia-owl' before

Question

Trying to re-use this script which used to work before, but it gives errors now:

Virtuoso 37000 Error SP030: SPARQL compiler, line 5: Undefined namespace prefix at 'dbpedia-owl' before 'dbpedia-owl:SportsTeam'

and the script itself:

select ?a ?b ?super (?aLength + ?bLength as ?length)
{
  values (?a ?b) { (dbpedia-owl:Person dbpedia-owl:SportsTeam) }

  { select ?a ?super (count(?mid) as ?aLength) { 
      ?a rdfs:subClassOf* ?mid .
      ?mid rdfs:subClassOf+ ?super .
    }
    group by ?a ?super
  }
  { select ?b ?super (count(?mid) as ?bLength) { 
      ?b rdfs:subClassOf* ?mid .
      ?mid rdfs:subClassOf+ ?super .
    }
    group by ?b ?super
  }
}
order by ?length
limit 1

Any ideas how to update it?

Answer 1

The namespace dbpedia-owl is not a prefixed namespace in DBPedia.

If you know the URL for the namespace, you can use PREFIX dbpedia-owl: <NAMESPACE_URL> before the SPARQL query. But if you're looking for DBpedia resource definitions of Person and SportsTeam, then you should be using (perhaps) dbo instead of dbpedia-owl.

Answer 2

dbpedia-owl: is not currently a predefined namespace prefix on DBPedia, though it once was. It has been replaced by dbo:.

As things stand, you can either change all instances of dbpedia-owl: in your queries to dbo:, or add this to the start of your queries --

PREFIX  dbpedia-owl:  <http://dbpedia.org/ontology/>

The latter is recommended.

For best results, you should always include PREFIX declarations in your SPARQL, instead of relying on such server-side predefinitions. This avoids any problems if namespace predefinitions are removed (as in this case) or changed to new URLs, which could have unpredictable effect on your query results.