从sparql查询结果中过滤掉某些属性

Question

I'm trying to filter out certain properties (eg dbpprop: ones) from the result of a sparql query. I'm querying dbpedia sparql endoint.

More precisely what I'd like to do is expressed by the following pseudo code :

quantity_of_interest, property, value, property_type = sparqlQuery(query)
if property_type == rdf:Property:
    pass
else:
    return quantity_of_interest, property, value

For now, I filter out the properties afterwards in some python code and I use the following sparql query :

SELECT DISTINCT ?qoi ?property ?value (bif:either(?type=rdf:Property, 0, 1) as ?filter_out) 
WHERE { 
    ?qoi a foaf:Person. ?qoi ?property ?value. 
    OPTIONAL{?property rdf:type ?type }
}

If filter_out == 0 I discard the whole result.

Is there a way I can directly make a sparql query which filters out the whole result whenever ?type == rdf:Property ?

Answer 1

This one is working for me at http://dbpedia.org/snorql/?query=

PREFIX dbo: <http://dbpedia.org/ontology/>

SELECT DISTINCT ?qoi ?property ?value
WHERE { 
    ?qoi a foaf:Person. 
    ?qoi ?property ?value. 
OPTIONAL{ 
    ?property rdf:type ?type 
FILTER( ?type != "rdf:Property" ) }
}
LIMIT 100

I am not sure if this is the answer you are looking for

Answer 2

You can filter out dbprop: properties,

I'm trying to filter out certain properties (eg, dbpprop: ones) from the result of a SPARQL query. I'm querying the DBpedia SPARQL endpoint.

If you're binding properties in your result set, and you want to exclude ones whose URI begins with the dbpprop: prefix, you can do that with

filter(!strstarts(str(?p),str(dbpprop:)))

or you can filter out properties that don't have type rdf:Property .

Your pseudocode looks like it's doing something slightly different though:

quantity_of_interest, property, value, property_type = sparqlQuery(query)
if property_type == rdf:Property:
    pass
else:
    return quantity_of_interest, property, value

Every property could have the type rdf:Property , since it's the class of RDF properties. DBpedia might not have the triple

 p rdf:type rdf:Property 

for each property p , of course, so you may still be able to filter things out like this. If that's what you want to do, you can do it with filter not exists { … } :

filter not exists { ?p rdf:type rdf:Property }

For DBpedia, it's the same right now,

As it turns out, these will have the same effect on DBpedia, since there are no properties that have type rdf:Property and aren't also dbpprop: properties; the following query returns 0 :

select (count(*) as ?num) where {
 ?p a rdf:Property
 filter( !strstarts( str(?p), str(dbpprop:) ) )
}
limit 100

but one option is more future compatible.

I'd strongly suggest using the strstarts filter rather than the not exist here, though. While the URI of a property can't change over time (ie, a URI is constant), the triples about it can change. Thus, if you filter out dbpprop: properties, then you'll never accidentally filter out more than you're expecting. However, if you filter out things that have rdf:Property as a type, then you can easily lose results in the future if more p rdf:type rdf:Property triples are added (and it seems like such an addition would be logically compatible).