Hi, Arsham -- On Jul 1, 2014, at 02:53 PM, Arsham Mesbah <ars...@uga.edu> wrote:
> I have synthetic data generated using Lehigh University > Benchmark (LUBM) data generator (version 1.7), this > generates about 402 .owl file including the schema. > I sorted and distributed the triples based on the > predicate to 4 different servers. All of these servers > run Virtuoso. First question, key to everything that follows... Are you running Virtuoso Commercial Edition, or Open Source? Please check and provide the complete version string(s) for all instances (no need to repeat when it's identical) -- that is, the first paragraph of output from the relevant command -- Commercial Edition virtuoso-t -? Open Source Edition virtuoso-iodbc-t -? Are all servers involved in the federated query running the same version? What about the one that holds the complete data set? Are they all configured identically? Presuming not, what are the differences, in INI file and/or hosting environments? > I also have another server that holds the entire data set. > When I run the following query on the server that holds > the entire data, 59 triples are returned. This query is > query number 2 of the test queries provided with the LU > benchmark. > > > PREFIX rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#> > PREFIX rdfs: <http://www.w3.org/2000/01/rdf-schema#> > PREFIX ub: <http://cs.uga.edu#> > SELECT ?X, ?Y, ?Z > FROM <http://www.cs.uga.edu#> > WHERE > { > ?X rdf:type ub:GraduateStudent . > ?Y rdf:type ub:University . > ?Z rdf:type ub:Department . > ?X ub:memberOf ?Z . > ?Z ub:subOrganizationOf ?Y . > ?X ub:undergraduateDegreeFrom ?Y > } > > I wrote a federated version of this query based on my > triple distribution and ran in on the distributed version. > However only 1 triple is returned. I grabbed few of the > triples returned from the single server version and > checked if data needed for these triple to be returned > exist on the distributed version of the data and it does, > however it is not returned as a result. The federated > query is the following: > > > PREFIX rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#> > PREFIX rdfs: <http://www.w3.org/2000/01/rdf-schema#> > PREFIX ub: <http://cs.uga.edu#> > SELECT * > WHERE > { > SERVICE <http://IPADD/sparql> { > ?X rdf:type ub:GraduateStudent . > ?Y rdf:type ub:University . > ?Z rdf:type ub:Department . > ?X ub:undergraduateDegreeFrom ?Y > } > SERVICE <http://IPADD/sparql> { > ?X ub:memberOf ?Z . > } > ?Z ub:subOrganizationOf ?Y . > } Is this exactly the query you've been running? As I read it, this query will involve 2 Virtuoso instances, in three phases. Both remote subqueries go to the same endpoint -- <http://IPADD/sparql> -- and the third is on the local endpoint. Given your description of your test, I think you *probably* meant for the remote portions to target *different* service endpoints, even if no other change is needed. > Also, if I move the last triple pattern on the federated > query ?Z ub:subOrganizationOf ?Y . up to I get the > following error: Virtuoso RDFZZ Error DB.DBA.SPARQL_REXEC > ('IPADD/sparql', ...) has received result with unexpected > variable name 'stubvar15' My understanding of the federated > query is that it gets all the triples returned by triple > patterns in the query and by service clauses in the query > and joins them if possible, therefore moving a triple > pattern up or down should not affect the result of the > query. Am I missing anything here? I think we come back to this after the above sections. Regards, Ted > -- > Kind Regards, > ~A -- A: Yes. http://www.guckes.net/faq/attribution.html | Q: Are you sure? | | A: Because it reverses the logical flow of conversation. | | | Q: Why is top posting frowned upon? Ted Thibodeau, Jr. // voice +1-781-273-0900 x32 Senior Support & Evangelism // mailto:tthibod...@openlinksw.com // http://twitter.com/TallTed OpenLink Software, Inc. // http://www.openlinksw.com/ 10 Burlington Mall Road, Suite 265, Burlington MA 01803 Weblog -- http://www.openlinksw.com/blogs/ LinkedIn -- http://www.linkedin.com/company/openlink-software/ Twitter -- http://twitter.com/OpenLink Google+ -- http://plus.google.com/100570109519069333827/ Facebook -- http://www.facebook.com/OpenLinkSoftware Universal Data Access, Integration, and Management Technology Providers ------------------------------------------------------------------------------ Open source business process management suite built on Java and Eclipse Turn processes into business applications with Bonita BPM Community Edition Quickly connect people, data, and systems into organized workflows Winner of BOSSIE, CODIE, OW2 and Gartner awards http://p.sf.net/sfu/Bonitasoft _______________________________________________ Virtuoso-users mailing list Virtuoso-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/virtuoso-users
