CODEWITHSUNDEEP
sparqlvirtuosoinference
N00bsie
N00bsie

Reputation: 469

Default RDFS inference in Virtuoso 7.x

This is a question about simple RDFS inference in Virtuoso 7.1 and DBpedia. I have a Virtuoso instance which was installed using this link as a reference. Now if I query the endpoint with the following query : 

Select ?s 
where { ?s a <http://dbpedia.org/ontology/Cricketer> . }

I get a list of Cricketers that are present in DBpedia. Suppose I want all the athletes (all sports and cricketers included, where Athlete is rdfs:superClassOf Cricketer), I just try the query 

Select ?s 
where { ?s a <http://dbpedia.org/ontology/Athlete> . }

For this I get all the correct answers. However I have an issue with rdfs:subPropertyOf. For example the property <http://dbpedia.org/ontology/capital> is the sub-property of <http://dbpedia.org/ontology/administrativeHeadCity>. So suppose I want all the capitals and the administrative head cities and I issue the query 

Select ?s ?o 
where { ?s <http://dbpedia.org/ontology/administrativeHeadCity> ?o . }

I get zero results. Why is it that subproperty inference isn't working in DBpedia? Is there something else that I have missed?

Upvotes: 1

Views: 424

Answers (2)

UninformedUser
UninformedUser

Reputation: 8465

There is no automatic inference enabled in DBpedia. DBpedia itself is a dataset loaded into Virtuoso.

The reason that you get all instances with a superclass like dbo:Athlete is that subclass-inheritance is fully materialized in the current DBpedia dataset:

(s rdf:type c1), (c1 rdfs:subClassOf c2) -> (s rdf:type c2)

That means that for each individual x, the DBpedia dataset contains all the classes C it belongs to - in fact also the superclasses.

That procedure was not done for subproperty-inheritance, i.e.,

(s p1 o), (p1 rdfs:subPropertyOf p2) -> (s p2 o)

You can solve that problem with SPARQL 1.1 property paths:

SELECT ?s ?o WHERE {
   ?p rdfs:subPropertyOf* <http://dbpedia.org/ontology/administrativeHeadCity> .
   ?s ?p ?o .
}

Upvotes: 2

TallTed
TallTed

Reputation: 9434

You've missed a couple of things.

First, Virtuoso is at 7.2.4 as of April 2016, and this version is strongly recommended over the old version from 2014, for many reasons.

@AKSW's advice about Property Paths will work much better with this later version, too.

Then, you can use inference on the DBpedia endpoint (including your local mirror), through the input:inference pragma, as shown on the live results of the query shown below --

DEFINE input:inference "http://dbpedia.org/resource/inference/rules/dbpedia#"

SELECT ?place ?HeadCity 
WHERE
  {
     ?place  <http://dbpedia.org/ontology/administrativeHeadCity>  ?HeadCity
  }
ORDER BY ?place ?HeadCity

You can also see a list of predefined inference rule sets.

And... more of the relevant documentation.

(ObDisclaimer: I work for OpenLink Software, producer of Virtuoso.)

Upvotes: 2

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