SPARQL: Multiple facets in one query

sparql_multiple_facets_one_query.sparql

# This SPARQL query could be used to calculate facets for SPARQL result set.
# The base result is defined as a subquery.
# Facets are calculated for the result set, and are returned as rows consisting of a facet id, a label,
# and a count.
# This query works against Virtuoso SPARQL endpoints.
# You can try it the against dbpedia virtuoso sparql endpoint, but it will probably fail due to the DBPedia endpoint's
# performance limitations.

PREFIX rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#>
PREFIX rdfs: <http://www.w3.org/2000/01/rdf-schema#>
PREFIX dbp: <http://dbpedia.org/property/>
PREFIX dbo: <http://dbpedia.org/ontology/>

# select the facet key, the facet value, and the facet count
SELECT distinct ?key ?facet_label ?facet_count
WHERE 
{

 { # facets
  { # position facet
   SELECT distinct ('position') as ?key ?position as ?facet_label count(distinct ?s) as ?facet_count
   WHERE{
    {?s dbo:position ?position} .
   }
  } # end position facet

  UNION

  { # country facet
   SELECT distinct ('country of birth') as ?key ?country as ?facet_label count(distinct ?s) as ?facet_count
   WHERE{
    {?s dbp:countryofbirth ?country} .
   }
  } # end country facet

 # ... other facets ...

 } # end facets

 .

 # subquery for base set for which facet counts will be calculated

 { 
  SELECT distinct ?s
  WHERE
  {
   {<http://dbpedia.org/resource/Arsenal_F.C.> dbp:name ?s} .
   {?s rdf:type dbo:Person}.
  }
 }  # End base set selection

} # End