Silk Single Machine can not find SPARQL Endpoint of 4store

[Rafael - MIchael Karampatshs]

Hello!
I 've been using the latest version of Silk Single Machine for some
time but recently i have been experiencing the following problem.

I have a 4store server running locally and a Sparql endpoint running
on it. Link: http://4store.org/
I 'm trying to perform some queries on the Sparql endpoint using SILK
but i keep getting the following error :

INFO: Query on http://localhost:8000/sparql failed:
SELECT DISTINCT ?a
WHERE {
?a <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> <http://
www.w3.org/2002/07/owl#Thing> .
} OFFSET 0 LIMIT 1000
Error Message: '500 SPARQL protocol error
This is a 4store SPARQL server v1.1.3'.
Retrying in 1000 ms. (2/3)
May 23, 2012 5:38:30 PM
de.fuberlin.wiwiss.silk.util.sparql.RemoteSparqlEndpoint
$ResultTraversable de$fuberlin$wiwiss$silk$util$sparql
$RemoteSparqlEndpoint$ResultTraversable$$executeQuery
INFO: Query on http://localhost:8000/sparql failed:
SELECT DISTINCT ?a
WHERE {
?a <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> <http://
www.w3.org/2002/07/owl#Thing> .
} OFFSET 0 LIMIT 1000
Error Message: '500 SPARQL protocol error
This is a 4store SPARQL server v1.1.3'.
Retrying in 1000 ms. (3/3)
May 23, 2012 5:38:31 PM de.fuberlin.wiwiss.silk.LoadTask$LoadingThread
run
WARNING: Error loading resources
java.io.IOException: Server returned HTTP response code: 500 for URL:
http://localhost:8000/sparql/
at
sun.net.www.protocol.http.HttpURLConnection.getInputStream(HttpURLConnection.java:
1436)
at de.fuberlin.wiwiss.silk.util.sparql.RemoteSparqlEndpoint
$ResultTraversable.de$fuberlin$wiwiss$silk$util$sparql
$RemoteSparqlEndpoint$ResultTraversable$
$executeQuery(RemoteSparqlEndpoint.scala:99)
at de.fuberlin.wiwiss.silk.util.sparql.RemoteSparqlEndpoint
$ResultTraversable.foreach(RemoteSparqlEndpoint.scala:50)
at de.fuberlin.wiwiss.silk.util.sparql.SimpleEntityRetriever
$EntityTraversable.foreach(SimpleEntityRetriever.scala:136)
at
de.fuberlin.wiwiss.silk.cache.FileEntityCache.write(FileEntityCache.scala:
43)
at de.fuberlin.wiwiss.silk.LoadTask$LoadingThread.run(LoadTask.scala:
91)
May 23, 2012 5:38:31 PM de.fuberlin.wiwiss.silk.util.task.Task$class
liftedTree1$1
WARNING: Loading failed


I can perform queries on the endpoint through it's test page :
http://localhost:8000/test/
Also i can perform queries on http://localhost:8000/sparql/ using an
external library like :
https://github.com/mhgrove/4Store-API/
I have also try using the dbpedia endpoint and a local open-rdf sesame
endpoint and they both worked fine!
Is this a bug or ....

Thanks a lot for your time!
Michael.

[Robert Isele]

Hi Rafael,

it is difficult to tell what goes wrong here. Quick googling of "500
SPARQL protocol error" reveals that this is a frequent problem with
4store. Did you check if any of the mentions on google relate to your
problem?

Cheers,
Robert