Sparql about dbpedia:World_Wide_Web

问题

I'm new to the semantic web and I'm trying to figure out how to write a SPARQL query to extract from dbpedia everything about a particular subject. Not just it's proprieties, but also everything related to it.

I'm not even sure how to start such a query.

I would like to get all triples about the World Wide Web.

PREFIX dbpedia: <http://dbpedia.org/resource/>

SELECT DISTINCT ?s ?p ?o 
WHERE  {
  ?s ?p ?o .
  ?s ?p dbpedia:World_Wide_Web  

  #  FILTER( lang(?s) = "en" )   -- doesn't work with filter

}Limit 100

This only returns some triples with a owl:sameAs predicate

Can you help me?

回答1:

You can get all the triples that have dbpedia:World_Wide_Web as their subject or object with a query like this (this only gives 1000, of course). For any objects that are literals, we can restrict their language value:

select ?s ?p ?o where {
  values ?web { dbpedia:World_Wide_Web }
  { ?web ?p ?o bind( ?web as ?s ) } union
  { ?s ?p ?web bind( ?web as ?o ) }

  # for literal objects, take only English ones
  filter( !isLiteral(?o) || langMatches(lang(?o),'en') )
}
limit 1000

SPARQL results

This includes results like the following, which seems to align with what you mentioned in the comments:

http://dbpedia.org/resource/World_Wide_Web  http://dbpedia.org/property/company  http://dbpedia.org/resource/CERN
http://dbpedia.org/resource/World_Wide_Web  http://dbpedia.org/property/inventor  http://dbpedia.org/resource/Tim_Berners-Lee

That will produce a lot of results, so you might want to restrict the properties that you can use. You should be able to do the following, but on the current DBpedia endpoint, it causes an error.

select ?s ?p ?o where {
  values ?web { dbpedia:World_Wide_Web }
  values ?p   { rdf:type dbpedia-owl:abstract }

  { ?web ?p ?o bind( ?web as ?s ) } union
  { ?s ?p ?web bind( ?web as ?o ) }
}
limit 1000

Virtuoso 37000 Error SP031: SPARQL compiler: Internal error: sparp_gp_attach_filter_cbk(): attempt to attach a filter with used variable

SPARQL query:
define sql:big-data-const 0 
#output-format:text/html
define sql:signal-void-variables 1 define input:default-graph-uri <http://dbpedia.org> select ?s ?p ?o where {
  values ?web { dbpedia:World_Wide_Web }
  values ?p   { rdf:type dbpedia-owl:abstract }

  { ?web ?p ?o bind( ?web as ?s ) } union
  { ?s ?p ?web bind( ?web as ?o ) }
}
limit 1000

Instead, as a workaround, you can do this:

select ?s ?p ?o where {
  values ?web { dbpedia:World_Wide_Web }

  { ?web ?p ?o bind( ?web as ?s ) }
  union
  { ?s ?p ?web bind( ?web as ?o ) }

  filter( ?p in (rdf:type, dbpedia-owl:abstract ))  ###
}
limit 1000

SPARQL results

来源：https://stackoverflow.com/questions/21002440/sparql-about-dbpediaworld-wide-web

标签

sparql

dbpedia