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Re: Reification and Provenance modelling

From: Richard Cyganiak <richard@cyganiak.de>
Date: Sat, 17 Sep 2011 17:27:18 +0200
Cc: public-rdf-comments@w3.org
Message-Id: <7C0491DA-8141-4963-B9D7-62FED1B7B94E@cyganiak.de>
To: Bob Ferris <zazi@smiy.org>
Hi Bo,

Thanks for the response. More questions inline.

On 15 Sep 2011, at 17:46, Bob Ferris wrote:
> The proposal in the RDF Datasets proposal document [1] lacks the ability to elegantly deal with one-triple-graphs.

I don't follow. As far as I can tell, [1] works equally well regardless of the number of triples in the graph. In what way is the handling of single-triple graphs inferior to the handling of multi-triple graphs in this proposal?

> Single statements should make use of statement identifier instead.

Why?

> The simple graph literals proposal [4] looks a bit more elegant, however, these graphs have still no identifier (from my POV).

Why is this a problem? Note that you can make statements about them.

> All these proposals cannot deal with the "Slicing datasets according to multiple dimensions" [5].

I don't think that's true. The same triple can exist in multiple graphs. Nothing stops a triple store from providing different views on the same set of triples.

> The goal should be to develop a representation that do not require much additions to the existing triple-based model, i.e., (from my POV) adding an optional fourth element that represents a statement identifier.

[1] and [4] don't change the triple-based model *at all*. ([1] adds a formalism for handling multiple RDF graphs. [4] adds a new kind of RDF term within the triple-based model.)

In terms of the magnitude of the change, both of these are less invasive than [3].

> To preserve the triple-based nature of RDF we should develop a graph vocabulary that describes a graph, e.g., which statements are included etc.
> 
> This modelling has the following advantages (at least):
> - graphs can be indexed separately in triple stores

This is possible, and easier, in [1]. (And probably in [4], but I won't argue that case here.)

> - statements can be utilised in multiple graphs

This is possible in [1].

> - provenance for statements and graphs can be handled in a unified way.

This is possible in [1] if one thinks of a statement as a single-triple graph.

Best,
Richard




> 
> Cheers,
> 
> 
> Bo
> 
> 
> [1] http://www.w3.org/2011/rdf-wg/wiki/TF-Graphs/RDF-Datasets-Proposal
> [2] http://www.w3.org/2011/rdf-wg/wiki/TF-Graphs/RDF-Quadless-Proposal
> [3] http://lists.w3.org/Archives/Public/public-rdf-wg/2011Aug/0105.html
> [4] http://www.w3.org/2009/07/NamedGraph.html
> [5] http://www.w3.org/2011/rdf-wg/wiki/TF-Graphs-UC#Slicing_datasets_according_to_multiple_dimensions
> 
Received on Saturday, 17 September 2011 15:28:07 GMT

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