Re: [namedgraphs] SPARQL over named graphs with blank nodes

[Jennifer C. <jen...@at...>]

This probably is not related to the issues you are seeing, but it might be
worth noting.

Previously I had some problems in a particular use case including NG4J.
Eventually tracked them down to the NG4J-provided parser for TriX.  It
appears that TriX is not fully supported by the parser.  The problems were
completely resolved by a single change - using TriG instead of TriX.  

This was not a matter of incorrectly written TriX on our system's part.
Rather, we were beginning with a named graph model, writing as TriX and
later reading in the TriX - all done using NG4J.  

Jennifer
 

-----Original Message-----
From: Blom, J.J.C. (Jaap) [mailto:jb...@cr...] 
Sent: Friday, June 25, 2010 10:08 AM
To: ng4...@li...
Subject: Re: [namedgraphs] SPARQL over named graphs with blank nodes

Hi again,

Sorry forgot about this for a bit.

<snip>
> But only for debugging purposes. Right? I mean, this data is meant to be
processed automatically and an application doesn't care about labels.
</snip>

Well if that means that running in debugging mode actually enables bugs,
that may not be the best approach. Since I had the choice of keeping the
TRIX a bit readable or putting in labels that seemed to cause errors (not
sure why and the details have since escaped me). So now I declare logical
named blank nodes everywhere (assuming ARQ would hold itself to the
principles of RDF). So I may want to turn back on that decision.

<snip>
> I don't see a problem here. If you import such data into a Jena Model
(or
> Graph) then Jena automatically creates unique blank node identifiers.
</snip>

Well actually I import it in TriX for transporting and I checked, that
means the blank node labels aren't renamed. So that means I would need to
loop through all the named graphs and do it. Not something I would want to
implement for such a thing tbh.

<snip>
> Yes, I think it is a problem in Jena. NG4J uses the Jena implementation
of triple pattern matching over a union of RDF graphs which is implemented
in > > the 'MultiUnion' class (package 'com.hp.hpl.jena.graph.compose');
more precisely, the method 'multiGraphFind'
</snip>

Kay, thanks.

Greetings,
  Jaap Blom

http://www.croon.nl/disclaimer
http://www.croon.nl/inkoopvoorwaarden
Kamer van Koophandel Rotterdam nr. / Chamber of Commerce Rotterdam no.:
24002312

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