My Opera
Opera SPARQL Query Engine
This experimental server supports the SPARQL Query language for RDF. It has a partial SPARQL Protocol implementation, i.e. it supports the HTTP access method. On the backend, it uses the latest release of Redland/Rasqal and so, inherits the capabilities and limitations of that library.
The model is built from My Opera public data and consists of around 15 million triples.
Please note: The SPARQL Query Engine is currently offline.
Note that too complex queries will currently result in a "Proxy Error", while malformed queries will result in a pure-text error message.
Examples
SPARQL is a language still under construction by the W3C and not many are familiar with it. Therefore, let's have a look at some examples. You can write a query in the text field above, and it will return an XML document with your results.
To find the blog of a specific user, in this example chaals, launch the following query:
PREFIX foaf: <http://xmlns.com/foaf/0.1/>
SELECT ?blog WHERE
{ ?user foaf:nick "chaals" .
?user foaf:weblog ?blog . }
And now for a more complex example: To find the name, the address and the title, where they exist, of things created by the user by the nick haavard, use this query:
PREFIX foaf: <http://xmlns.com/foaf/0.1/>
PREFIX dc: <http://purl.org/dc/elements/1.1/>
SELECT ?creator ?post ?title WHERE { ?user foaf:nick "haavard" .
OPTIONAL { ?user foaf:name ?creator . }
OPTIONAL { ?post foaf:maker ?user . }
OPTIONAL { ?post dc:title ?title . }
}