Hello Hugh and everyone,
You can find the answers to your questions below.
I've already tried to use the HTTP Client Java API from Apache to
communicate with Virtuoso (with a POST method): all the queries seem
here to work perfectly, including the "cursed" one.
When I got on the Virtuoso Jena Provider, I've realized that the same
job could be done with 3 lines of code.
The choice actually depends on the reliability of the API.
Best regards,
*Marco FOSSATI
*Research and Development Engineer
*Arisem* /a Thales company///
1-5, Avenue Carnot
91883 Massy Cedex
Tél. : +33 01 69 75 30 24
Fax : +33 01 69 75 31 56
www.arisem.com <http://www.arisem.com/>
Hugh Williams wrote:
Hi Marco,
I have tested the query you report against a local DBpedia 3.5.1
Instance we have in-house via the Virtuoso Jena Provider and it runs
fine for me. It is specifically the addition of the order by in the
query that results in the problem on your machine ?
Yes, I've tried to run the query without the ORDER BY clause and it
works fine.
I' ve also found that the problem deals with the foaf:name property and
NOT with the rdfs:label one.
For example, this query WORKS:
SELECT ?test WHERE {
<http://dbpedia.org/resource/Unreal_II:_The_Awakening>
<http://www.w3.org/2000/01/rdf-schema#label> ?test } ORDER BY ?test
This query DOESN'T:
SELECT ?test WHERE {
<http://dbpedia.org/resource/Unreal_II:_The_Awakening>
<http://xmlns.com/foaf/0.1/name> ?test } ORDER BY ?test
N.B.: All the queries WORK if launched from the SPARQL endpoint, but not
via Java.
What Virtuoso release are you running as I have seen the "Tag 20 not
defined" error with earlier v5 builds from about a year ago but that
issue has long since been resolved and does not occur with the
components shipped with the latest v6 product or those from the
VOSDownload page link you refer to below. If you have been using
multiple Virtuoso versions please ensure their is only the one
virt_jena and virtjdbc3 jar files on the system and that you are not
picking up an old version.
I'm running the Virtuoso Open Source Edition (multi threaded), Version
6.1.1.3127, Build Apr 4 2010, Compiled for Linux (x86_64-pc-linux-gnu),
on a Debian Lenny distro.
I firstly downloaded the sources tarball from the web, but I encountered
problems when trying to compile them; I found then a Debian package in
the Sid repository and easily installed it.
The Virtuoso open source and commercial products use the same Virtuoso
Jena Provider, thus the link you used below does give you the official
commercial provider. Their are no Maven repositories for it, the
source are available in the open source archive (~/binsrc/jena) ,
should you want to access them ...
Best Regards
Hugh Williams
Professional Services
OpenLink Software
Web: http://www.openlinksw.com
Support: http://support.openlinksw.com
Forums: http://boards.openlinksw.com/support
Twitter: http://twitter.com/OpenLink
On 24 May 2010, at 10:24, Marco FOSSATI wrote:
Hello,
I'm working with the Virtuoso Jena Driver API to query a local
DBpedia ontology and process information with Jena API.
When launching a query with an ORDER BY clause, the following
exception is thrown:
Exception in thread "main" com.hp.hpl.jena.shared.JenaException: Can
not create ResultSet.:virtuoso.jdbc3.VirtuosoException: Tag 20 not
defined.
Here an example of SPARQL query that won't work:
SELECT ?title
WHERE { { <http://dbpedia.org/resource/Unreal_II:_The_Awakening>
<http://xmlns.com/foaf/0.1/name> ?title } UNION {
<http://dbpedia.org/resource/Unreal_II:_The_Awakening>
<http://www.w3.org/2000/01/rdf-schema#label> ?title } }
ORDER BY ?title
I found the virt_jena and virtjdbc3 jars in the OpenSource Virtuoso
Wiki (here
<http://virtuoso.openlinksw.com/dataspace/dav/wiki/Main/VOSDownload#Jena>).
As I'd like to use them in my application, I'm wondering if there is
an official release of this API, if it is maintained and if there is
any Maven 2 artifact set.
Best regards,
*Marco FOSSATI
*Research and Development Engineer
*Arisem* /a Thales company///
1-5, Avenue Carnot
91883 Massy Cedex
Tél. : +33 01 69 75 30 24
Fax : +33 01 69 75 31 56
www.arisem.com <http://www.arisem.com/>
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