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Re: Putting metadata in the "default" graph Re: Dataset Syntax - checking for consensus

From: Steve Harris <steve.harris@garlik.com>
Date: Thu, 27 Sep 2012 10:26:18 +0100
Cc: David Wood <david@3roundstones.com>, W3C RDF WG <public-rdf-wg@w3.org>
Message-Id: <B9B08B6A-02E5-4B4A-9416-5A56BEDB91A9@garlik.com>
To: Lee Feigenbaum <lee@thefigtrees.net>
On 2012-09-26, at 17:41, Lee Feigenbaum wrote:

> On 9/26/2012 12:09 PM, David Wood wrote:
>> * Some designs for carrying for metadata
>> PROPOSED: In our dataset syntax, we'll say that metadata goes in the default graph
>> +0.5, especially if it can be aligned with SPARQL service descriptions.
> What do existing systems do when importing a TriG file that contains data in the "default" graph? The Anzo store has no default graph, and therefore either throws an error or throws away any information in a TriG "default graph". Similarly, all TriG exported from Anzo does not have a default graph unless it's the serialization of a SPARQL RDF dataset (which by definition does have a default graph, of course).
> I bring this up because I brought up a related thread on public-sparql-dev recently:
> http://lists.w3.org/Archives/Public/public-sparql-dev/2012JulSep/0025.html
> In that thread, I asked:
> """
> Do all quad stores  / named graph stores include a default graph? If the store that you develop or use does have a default graph, does that graph also have a name (URI)?
> """
> The answers were:
> Anzo -- no default graph (except ones assembled on the fly for querying).
> OWLIM -- has a default graph with no URI
> RDF::Query -- has a default graph with no URI
> 4store & 5store -- default graph is a view on existing graphs (& therefore, I assume, doesn't exist for purposes of storing data) -- uses a "special" named graph for writing default data
> TDB -- can either have an actual default graph or just use the default graph as a view onto the other named graphs
> Additionally, there was input from 3 implementers (SteveH, GregW, and Chime) that if they could re-implement their systems they would not include a default/unnamed graph.
> All of which is to say, I think there's a fair amount of evidence that the "default" or unnamed graph is not consistently used, and perhaps not widely used. We need to support it for compatibility, but I think it's a mistake to specify that anything important be put in that graph.


- Steve

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Received on Thursday, 27 September 2012 09:26:49 UTC

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