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

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

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 It has been replaced by dbo:.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.

Answer 2

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.