Transitive DBPedia/virtuoso instance queries in sparql

Question

Is there a way to get from dbpedia's virtuoso's server all instances of a type <class> and of the subclasses of this <class>. I found some documentation about transitive queries in virtuoso but not sure how to use it.

If there isn't a way to get all of that with a single sparql query, what will then be the preferred query sequence?

Answer 1

Let me answer the question, notice the Inference rules link at the top left corner of dbpedia's sparql endpoint. Adding a reference to the inference set you want to use (as I understand it a graph where inference has already been executed) will add inferred results to your query. For example the query:

SELECT COUNT (*)
WHERE
{
  ?s  a  <http://dbpedia.org/class/yago/Church103028079>
}

returns 1790 results. While the same query using inference (below) returns 9065 results, taking into account instances of subclasses of cy:Church103028079.

define input:inference "http://dbpedia.org/resource/inference/rules/yago#"
SELECT COUNT (*)
WHERE
{
  ?s  a  <http://dbpedia.org/class/yago/Church103028079>
}

Answer 2

1

If Virtuoso supports SPARQL 1.1, you can do:

SELECT *
WHERE
{  ?cls rdfs:subClassOf* <http://dbpedia.org/class/yago/Church103028079> .
   ?inst a ?cls
}

answered Feb 03 at 11:47

scotthenninger
6.2k●8●13

I tried it and it doesn't unfortunately: http://dbpedia.org/sparql?default-graph-uri=http%3A%2F%2Fdbpedia.org&query=SELECT+*%0D%0AWHERE%0D%0A%7B++%3Fcls+rdfs%3AsubClassOf*+%3Chttp%3A%2F%2Fdbpedia.org%2Fclass%2Fyago%2FChurch103028079%3E+.%0D%0A+++%3Finst+a+%3Fcls%0D%0A%7D&format=text%2Fhtml&timeout=0&debug=on

(Feb 04 at 05:03) vladtn

it is not "rdfs:subClassOf*" but "rdfs:subClassOf" (that is: leave the wildcard)

(May 07 at 11:13) dr0i

1

ah - without the wildcard you get only one depth of subclasses and not all subclasses recursively. See http://www.w3.org/TR/sparql11-property-paths/

(May 08 at 06:39) dr0i

Answer 3

since virtuoso (and hence:dbpedia) doesn't implement all SPARQL 1.1 features, you can't go straight forward using property paths (as scotthenninger mentioned). If you need more than one depth of subclasses (recursively) - virtuoso has its own workaround, try this:


SELECT DISTINCT  COUNT (?x)  WHERE
{
{ SELECT ?x ?y WHERE { ?x rdfs:subClassOf ?y } }
OPTION ( TRANSITIVE, T_DISTINCT, t_in(?x), t_out(?y), t_step('path_id') as ?path, t_step(?x) as ?route, t_step('step_no') AS ?jump, T_DIRECTION 2 )
FILTER ( ?y = <http://dbpedia.org/class/yago/Church103028079> )
}

(source : following links in property paths in dbpedia benchmark )

This query shows up 2863 - thats the number of all distinct (direct and indirect) subclasses (and not: instances of subclasses as vladtn described) of yago:Church103028079,

Transitive DBPedia/virtuoso instance queries in sparql

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