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Re: why I don't like default graphs in the DATASET proposal

From: Richard Cyganiak <richard@cyganiak.de>
Date: Sun, 2 Oct 2011 13:18:44 +0100
Cc: Pierre-Antoine Champin <pierre-antoine.champin@liris.cnrs.fr>, "public-rdf-wg@w3.org" <public-rdf-wg@w3.org>
Message-Id: <7A75F0E4-0D55-4913-8FD2-1AA0819F1753@cyganiak.de>
To: Ian Davis <id@talis.com>
On 1 Oct 2011, at 17:53, Ian Davis wrote:
>>> But do you have a use case that would be solved by a dataset with
>>> default graph, that a dataset *without* default graph would *not* solve?
>> 
>> Backing up the contents of a SPARQL store as a dump, and loading it into a different SPARQL store.
> 
> Where is SPARQL store defined?

A store that supports SPARQL. Hence its data model is an RDF dataset.

> The reality is that most graph stores have names for all the graphs
> but designate one as the unnamed one for the purposes of SPARQL.

That's not true. Many stores have the union of all graphs in the default graph. In this common case the default graph isn't just a named graph designated as the default.

Also, SPARQL conformance doesn't require the model you describe.

What's more important: If the default graph isn't marked somehow in the dump file on export, then there's no way for the importing store to tell which of the named graphs it's supposed to use as the default.

That's why a dump format for SPARQL stores needs a marker for the default graph.

Best,
Richard
Received on Sunday, 2 October 2011 12:19:34 GMT

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