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Re: RDF-ISSUE-120 (set-of-triples-are-graphs): Is any set of RDF triples an RDF graph? [RDF Concepts]

From: Antoine Zimmermann <antoine.zimmermann@emse.fr>
Date: Thu, 14 Mar 2013 16:41:06 +0100
Message-ID: <5141EF92.1010507@emse.fr>
To: "Peter F. Patel-Schneider" <pfpschneider@gmail.com>
CC: public-rdf-wg@w3.org
Le 14/03/2013 15:54, Peter F. Patel-Schneider a écrit :
> I'm confused here.
>
> What do you see to indicate that a particular set of triples cannot form
> an RDF graph?

Pat saying it repeatledly. Last time was yesterday:

"An RDF graph is a set of triples **such that every bnode in the set is 
in a single bscope** (that is the second axiom), and we can then say 
that the graph is in the bscope."

In http://lists.w3.org/Archives/Public/public-rdf-wg/2013Mar/0125.html


> I assume that you are talking about issues of bnode scope.  However, I
> don't see anything in the discussion of bnode scope that prevents any
> particular set of triples from being an RDF graph. As far as I can tell,
> bnode scope could be completely removed from Semantics without changing
> anything.

So why does bnode scope even appear in Semantics if it has no impact?
What is it trying to solve?


> Yes, there is a change in the semantics. Previously the merge of RDF
> graphs involved changing bnodes as necessary. This is no longer the
> case, which does change how RDF works, but this change is being made to
> conform to practice.

In what way it align better with practice than before. In practice, 
bnodes are identified somehow, and the merge operation requires that 
nodes identifiers be "standardised apart" before uniting the graphs into 
one. This requirement would ne necessary, whether scopes are put in the 
abstract syntax or not.

This is not bringing a solution to an existing problem, and it's 
certainly not repairing something broken.

What applications need is a way to determine whether some triples have 
to be considered as forming one graph, as opposed to forming several 
graphs. E.g., I have 2 NTriples files. Should I consider that they 
serialise two halves of a graph, or that they serialise two graphs? The 
application has to decide, but it shouldn't be the business of semantics 
to tell them how they do this.
Once the decision of partitioning the triples into graphs (or in one 
graph for that matter) the semantics of 2004 applies straightforwardly.

BTW, I would like to be able to put a single graph in multiple N-Triples 
files, because I want to be able to send huge RDF graphs in multiple 
packets.  So I would not be happy if the spec says that the scope is 
necessarily delimited by the file.


AZ.

>
> peter
>
> On 03/14/2013 02:39 AM, RDF Working Group Issue Tracker wrote:
>> RDF-ISSUE-120 (set-of-triples-are-graphs): Is any set of RDF triples
>> an RDF graph? [RDF Concepts]
>>
>> http://www.w3.org/2011/rdf-wg/track/issues/120
>>
>> Raised by: Antoine Zimmermann
>> On product: RDF Concepts
>>
>> All work on RDF until early 2013 have been made under the assumption
>> that a set of RDF triples is an RDF Graph (and vice versa). Recent
>> discussions on bnode scope suggest that there are combinations of RDF
>> triples that do not form a graph. Precisely, the idea is that only the
>> triples that belong to the same "scope" (whatever that means) can be
>> in the same RDF graph.
>>
>> This also impact the definition of an RDF triple, as there can be two
>> blank nodes in the same triple.
>>
>>
>>
>
>
>

-- 
Antoine Zimmermann
ISCOD / LSTI - Institut Henri Fayol
École Nationale Supérieure des Mines de Saint-Étienne
158 cours Fauriel
42023 Saint-Étienne Cedex 2
France
Tél:+33(0)4 77 42 66 03
Fax:+33(0)4 77 42 66 66
http://zimmer.aprilfoolsreview.com/
Received on Thursday, 14 March 2013 15:41:36 UTC

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