virtuoso Questions - Semantic Overflow

Sort by date optimizations on large dataset

2010-07-08T13:31:16Z

I'm trying to get the most recent articles on a subject out of http://pubmed.bio2rdf.org/sparql. I can get a list of articles on a subject but as soon as I try to order by date the request times out.

This is the query I am using:

select ?s ?created ?title where 
{?s <http://bio2rdf.org/pubmed_resource:meshref> _:cite.
 _:cite <http://bio2rdf.org/pubmed_resource:descriptor> <http://bio2rdf.org/mesh:Neoplasms>.
 ?s <http://purl.org/dc/terms/created> ?created.
 ?s <http://purl.org/dc/terms/title> ?title.
 ?s <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> <http://bio2rdf.org/pubmed:JournalArticle>. 
}
order by desc (?created)

If I remove the order by clause I get resuts, with the order by clause it times out. I guess it is having to do a full text scan of the nodes does anyone have an idea how to optimize it?

Limit dosn't seem to make a difference.

I was thinking of limiting the graph, but it looks like each JournalArticle is a seperate graph.

How to set up a clustered Virtuoso on Debian/Ubuntu?

2010-06-23T12:42:22Z

Cygri mentioned in reply to the question Distributed triple stores that Virtuoso can be set up in a clustered mode. How would one do this using the Virtuoso that comes with Debian or Ubuntu? Please provide detailed configuration scripts.

How do I delete a named graph in Virtuoso?

2010-06-10T01:25:36Z

Hello,
This is a simple question but I couldn't find any information. Once I have loaded a graph using RDF_LOAD_XML_MT how do I go about delete it.

Thanks
Sandeep

Strange query-time estimation on dbpedia sparql endpoint

2010-06-06T20:10:44Z

Take these two queries:

SELECT distinct ?name WHERE {
    optional {
        ?redirect dbpedia2:redirect <http://dbpedia.org/resource/Lionel_Messi>.
        ?redirect rdfs:label ?name.
    } .
    optional { <http://dbpedia.org/resource/Lionel_Messi> foaf:name ?name } .
}


SELECT ?name WHERE {
    optional {
        ?redirect dbpedia2:redirect <http://dbpedia.org/resource/Lionel_Messi>.
        ?redirect rdfs:label ?name.
    } .
    optional { <http://dbpedia.org/resource/Lionel_Messi> foaf:name ?name } .
}

They differ only in the use of 'distinct' in the select. Note the dual use of the ?name variable (this is to make using the result easier). The bottom query work great on dbpedia, the top one nets a '42000 Error The estimated execution time 29959 (sec) exceeds the limit of 1500 (sec).' The size of the result is not very great, so the 'distinct' operation should not be costly.

I can distinctify the results just fine on my own, I'm just curious about the SPARQL engines' reasoning.

DBPedia SPARQL Endpoint xsd:date comparison weirdness

2010-06-04T14:08:53Z

I'm trying to find persons (soccer players) in DBPedia by name and birthdate. This returns one result (expected):

SELECT ?player ?birth
{
    ?player a dbpedia-owl:SoccerPlayer .
    ?player foaf:name "Daniel Agger"@en .
    ?player dbpedia2:birth ?birth .
    FILTER(?birth <= "1984-12-13"^^xsd:date) .
    FILTER(?birth >= "1984-12-11"^^xsd:date) .
}
Limit 10

This returns no results:

SELECT ?player ?birth
{
    ?player a dbpedia-owl:SoccerPlayer .
    ?player foaf:name "Daniel Agger"@en .
    ?player dbpedia2:birth ?birth .
    FILTER(?birth <= "1984-12-12"^^xsd:date) .
    FILTER(?birth >= "1984-12-12"^^xsd:date) .
}
Limit 10

Neither does this:

SELECT ?player ?birth
{
    ?player a dbpedia-owl:SoccerPlayer .
    ?player foaf:name "Daniel Agger"@en .
    ?player dbpedia2:birth ?birth .
    FILTER(?birth = "1984-12-12"^^xsd:date) .
}
Limit 10

Is there something about the semantics of xsd:date comparison I don't get or is this a bug?

How to get started with virtuoso universal server for rdf querying.

2010-04-16T07:49:46Z

How to get started with virtuoso universal server for rdf querying using sparql?

Comparisons of D2RQ and Virtuoso RDF Mapping?

2010-03-24T21:09:13Z

Are there any detailed comparisons between the mapping capabilities of D2RQ vs. those of the wrapper system built into Virtuoso? It seems that the D2RQ package is fairly complete, but it would be interesting to see if someone has compared them in-depth in the past.

Virtuoso Reasoner Problem

2010-02-15T23:17:08Z

I've run the following script against virtuoso CLI: sparql clear graph http://jenainftest/#;

ttlp('@prefix rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#>.
@prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#>.

@prefix contact: <http://www.sciresexamplerdf.com/contact#>.

contact:firstName
    rdfs:subClassOf rdfs:Property;
    rdfs:domain contact:Person.



contact:Person
    rdfs:subClassOf	rdfs:Class.
', '', 'http://jenainftest/#');

rdfs_rule_set ('jenainftest_ttl2', 'http://jenainftest/#', 0);

sparql
define input:inference 'jenainftest_ttl2'
select * where {?s ?v "B2_99" . ?s rdf:type <http://www.sciresexamplerdf.com/contact#Person>}
;

Input data was: contact:firstName "B2_99"

I would have expected to receive at least one row in response (due to Virtuoso inferring the type from the input data), however I received zero responses. Removing the type data from the query results in the expected number of results.

Is Virtuoso unable to infer type information based upon rdfs:properties?

How to speed up rdf:type foo:Bar SPARQL queries by Virtuoso tuning?

2010-01-15T19:32:50Z

I'm running SPARQL queries like:

prefix ch: <http://pele.farmbio.uu.se/chembl/?>

select count(?s) where {
  ?s a ch:Compound .
}

or any other 'a' query asking all Resources of a certain rdf:type, which is quite slow resulting in a time out... how can I get Virtuoso to be a bit speedier here? Can I index the store so that it more efficiently can return all resources rdf:type some:Foo?

Question about RDFizer Sponger in Virtuoso OpenLink Software

2009-11-22T17:59:38Z

Did any one here use Sponger cartridge available in virtuoso openlink software? I had installed virtuoso opensource triple store and am currently trying to use the sponger cartridge to convert an Atom feed into RDF/XML. I have an XSLT stylesheet for the transformation. The documentation provided for virtuoso-sponger says that Sponger is in built into SPARQL end point and that if a sparql query is written like say "select ?p from named http://example.com/atomfeed.xml option (get:soft "soft",get:method "GET") where {GRAPH ?g {?s ?p ?o}}", it would via HTTP go the specified link, call the sponger, extract the data and map it to a particular schema using a particular stylesheet. Now is it the GRDDL that should be used to point to the xsl stylesheet ? If I do not have a GRDDL tag in my atom feed how would I call a particular XSLT stylesheet? Can somebody who worked with virtuoso sponger help me in doing this. If you think this is not the relevant form to ask this question can you explain the importance of GRDDL.

Thanks

How do I see what named graphs are available on a Virtuoso SPARQL end point?

2009-11-02T20:31:19Z

Is it possible to list the named graphs using a SPARQL query?