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Re: TriG and default graphs

From: Pat Hayes <phayes@ihmc.us>
Date: Wed, 24 Oct 2012 12:25:43 -0500
Cc: <public-rdf-wg@w3.org>
Message-Id: <0383BB94-FBD6-4C6D-8938-4C197C9735A9@ihmc.us>
To: Yves Raimond <Yves.Raimond@bbc.co.uk>

On Oct 24, 2012, at 11:29 AM, Yves Raimond wrote:

> Hello!
> 
> Just jumping on the last point that was mentioned in today's telecon, about possibly not providing any statements about what to do with a TriG default graph. I have the feeling that not doing that actually defeats the point of having a default graph at all. 
> 
> If we can't get to an agreement on that first point, I'd really like to understand what the rationale is behind supporting default graphs in TriG, apart from backward-compatibility. When used at the BBC, default graphs have proven to be a very confusing feature, and not having any statement on what do with them would only add to the confusion. 

I think the rationale was that SPARQL queries might just be directed to a dataset without specifying a graph name, and the default was there to catch those queries. (The entire idea of datasets was introduced by the SPARQL group, so it reflects their concerns more than those of publishers.) The "default=metadata" meme came along later, and doesn't fit so well with the original motivation. 

> All the dataset metadata that is supposed to go in that default graph could perfectly go in another named graph, e.g. identified by the URI of the sd:Dataset in the SPARQL end-point you're generating a TriG dump from, or the URI of the TriG file itself. Personally, I'd favour a 'flat' version of TriG, where everything is a named graph.

Which also aligns better with the quad store model of datasets, of course. But again, quad stores were a new implementation detail when SPARQL was being conceptualized. 

Pat

> 
> Best,
> Yves
> 
> 
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Received on Wednesday, 24 October 2012 17:26:17 GMT

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