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Re: Using named graphs to model PROV's Accounts

From: Timothy Lebo <lebot@rpi.edu>
Date: Tue, 4 Oct 2011 14:10:38 -0400
Cc: public-rdf-prov@w3.org
Message-Id: <E32EA624-5BD6-45C3-9C77-C1B5A6936528@rpi.edu>
To: Richard Cyganiak <richard@cyganiak.de>
Hey, Richard!

Thanks for your comments. I responded with:

On Oct 4, 2011, at 10:21 AM, Richard Cyganiak wrote:

> On 3 Oct 2011, at 00:47, Timothy Lebo wrote:
>> I have written an initial proposal [1] for how to use RDF named graphs and PROV's OWL encoding to represent PROV's notion of an Account.
> “They are a feature of the non-standard N3 language [7] and are not widely used, perhaps because of verbosity and size considerations.” – N3 itself isn't widely used or implemented. That's sufficient explanation for the scarceness of graph literals. I'm not sure there's enough evidence to pinpoint specific reasons such as  “verbosity and size”.

Reasonable. I trimmed the reasons.

> “Named graphs surface in a variety of ways.” – I'd add another way: an RDF file published under a URI can be seen as a named graph in a global, web-wide named graph set.

Yes, I had considered including this, but figured I'd set the threshold a smidgen higher -- to keep the discussion moving.
Do you think I should include it for completeness?
I added a TODO in http://www.w3.org/2011/prov/wiki/Using_named_graphs_to_model_Accounts#Representing_a_named_graph

> “Sameness of named graphs” – The entire section seems questionable to me. It is true that nothing stops us from using the same graph name with different contents in different datasets, but this is equally true of any URI anywhere in RDF. As far as RDF Concepts and RDF Semantics are concerned, the URI ex:foo might represent one thing RDF graph G1 and something else in RDF graph G2 – it is only the social contracts and conventions around URI ownership and web architecture that discourage such behaviour and allow us to maintain the fiction that URIs in RDF actually identify specific entities. The same could be said of graph names.
> I'm sceptical about the assertion that a named graph's “last modified time” contributes to its identity. In the example, the last modified time of the individual graphs is unknowable. It perhaps makes sense to talk about a last modified name of the enclosing TriG file, but not of the graphs themselves.

I appreciate your feedback on both of these points. I added them to 
because I'm not quite sure where to put it right away while preserving your points.

> Instead of speaking of a graph's “location”, it might be more accurate to speak of the “RDF dataset” it is in. The term is defined in the SPARQL spec.

Thanks for the technical pointer. I'll look it up and incorporate.


>> [1] http://www.w3.org/2011/prov/wiki/Using_named_graphs_to_model_Accounts
Received on Tuesday, 4 October 2011 18:11:20 UTC

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