Error in SPARQL query URL "Undefined namespace prefix"

[akuckartz]

The phrase "results of SPARQL queries" in the first sentence of README.md is linked to

http://dbpedia.org/sparql?default-graph-uri=http%3A%2F%2Fdbpedia.org&query=CONSTRUCT+%7B+%3Fp+a+dbpedia-owl%3AArtist+%7D%0D%0AWHERE+%7B+%3Fp+a+dbpedia-owl%3AArtist+%7D&format=text%2Fturtle

Dereferencing that URL results in this error message:

Virtuoso 37000 Error SP030: SPARQL compiler, line 3: Undefined namespace prefix at 'dbpedia-owl' before '}'

SPARQL query:
define output:format "HTTP+TTL text/turtle" 
#output-format:text/turtle
define input:default-graph-uri <http://dbpedia.org> CONSTRUCT { ?p a dbpedia-owl:Artist }
WHERE { ?p a dbpedia-owl:Artist }