Accessing an EDG SPARQL endpoint from within another EDG instance..

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robatki...@gmail.com

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Jul 14, 2021, 12:32:12 AMJul 14
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I want to access live EDG content to download in a development context.  The export process gets out of hand if i have a bunch of graphs to sync, and the trig backup is too coarse grained if the live site has a lot of data, and neither allows me to control a subset with a select statement...

SELECT * 
WHERE
{ SERVICE <https:// example.org/edg/tbl/sparql
   {
    GRAPH <urn:x-evn-master:frogs_datagraph> 
  {?uc a :Frog } 
 
}


SELECT * 
WHERE
  {?uc a  :Frog    } 
 
}

Got this result..

Failed to execute SPARQL request: org.apache.jena.sparql.resultset.ResultSetException: Failed when initializing the StAX parsing engine

but if i access the local server

it works

So i presume its possibly related to permissions - and just a bad error message? 

If so, how can one set user permissions when accessing a remote endpoint?


Holger Knublauch

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Jul 15, 2021, 7:17:29 PMJul 15
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Hi Rob,

sorry for the delay as I had to ask a colleague. We also suspect it could simply be an authentication problem and the error is choking on the response. For authentication against the remote endpoint it will check the records available on the Password Management page, and if there is any that exactly matches the SERVICE URI, then that user name and password will be used with basic auth for making the request. So I believe your first example should work if you have a username/password for https://example.org/edg/tbl/sparql and then use the GRAPH keyword. I doubt the second variation with the ? argument will work.

If you could give that a try?

Holger

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Rob Atkinson

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Jul 15, 2021, 9:55:20 PMJul 15
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That makes sense - but didnt work when I tried it :-( 
Double checked it.

We can access the SPARQL endpoint from other locations via scripts, so shouldnt be a more systemic access problem.


Holger Knublauch

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Jul 15, 2021, 11:09:57 PMJul 15
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I don't know how to help further. The error is from within Jena code, and only a proper Java debugger or network monitor could find out where it's failing, e.g. what the remote server response is.

Holger

Rob Atkinson

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Jul 16, 2021, 12:45:54 AMJul 16
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ok i'll try to get a network monitor onto it..


an...@seaborne.org

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Jul 16, 2021, 3:50:44 AMJul 16
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The exception in question has a "cause" exception attached:

    throw new ResultSetException("Failed when initializing the StAX parsing engine", ex) ;

Any stacktrace will have that printed.

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