Why dbpedia result is not consistant

问题:

I'm executing the below SPARQL query

PREFIX rdfs: <http://www.w3.org/2000/01/rdf-schema#> 
SELECT ?resource WHERE  { 
?resource a <http://dbpedia.org/ontology/Place> . 
{?resource rdfs:label 'Paris'@en.} UNION { ?resource rdfs:label 'France'@en.} 
}

I'm executing this here. Sometimes I am getting required result and sometimes it returns 502 error ( I get the message that website is under maintenance.....) Can you please let me know why result is not consistent and how can I avoid this?

Also inconsistent behavior when I execute through java code :

       Query query = QueryFactory.create(sb.toString());
        QueryExecution qexec = 
          QueryExecutionFactory.sparqlService("http://dbpedia.org/sparql",  query);   

回答1:

The experimental DBpedia SPARQL endpoint is made available as a public service, but as such it has no Quality-of-Service (QoS) guarantees.

You can set up your own DBpedia mirror in the Amazon AWS cloud, by spinning up the pre-populated and dynamically updated AMI. You can also set up a local mirror, by manually loading the DBpedia datasets into your own Virtuoso or other triple or quad store instance.

(ObDisclaimer: OpenLink Software produces Virtuoso and the DBpedia AMI, provides and maintains the public DBpdia endpoint, and employs me.)