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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: Pat Hayes <phayes@ihmc.us>
Date: Fri, 15 Mar 2013 10:37:09 -0500
Cc: public-rdf-wg@w3.org
Message-Id: <EB9A06FD-6B0F-4E16-A588-9FB1EF5922CA@ihmc.us>
To: Antoine Zimmermann <antoine.zimmermann@emse.fr>

On Mar 14, 2013, at 1:17 PM, Antoine Zimmermann wrote:

> So, if I have a set of RDF graphs (say, in a specification based on RDF semantics) I do not have any concept from RDF that I can use to treat it as a single graph, as far as truth is concerned.

What?? No, this is nonsense. 

> Why should this be the case in RDF 1.1? What was fundamentally wrong with having such a notion? What is it trying to address?

It is not the case. I have no idea what you are thinking which can lead you to this idea.

> 
> Now, what is the truth of a set of triples? RDF 1.1 Semantics currently do not say, cf. the semantic condition on bnode assumes this:
> 
> """
> If E is an RDF graph then I(E) = true if [I+A](E) = true for some mapping A from the set of blank nodes in the scope of E to IR, otherwise I(E)= false.
> """
> 
> What is the scope of E when E contains bnodes from different scopes?

It cannot contain nodes from different scopes, by definition of "scope" (or by the axiom, if you like, which says that every RDF graph must have a single scope for its bnodes.)

> 
> The other thing is: what is the scope of the merge?

It is a new scope, defined by the document or structure which represents the merge. (Assuming we are talking about bnodeID scopes, as in the current draft text. If we were talking about bscopes, from my earlier email, then it would simply be a new bscope, which is why we would have the "copy" language. But let us keep that idea restricted to emails for now.)

> A complete graph has bnodes in only one scope. Therefore, the union of two different complete graphs is necessarily containing bnodes in different scopes. So merge creates non-scoped-graphs.

No, it creates a new scope to contain the merge. (Or, if this is possible, it could re-use another scope, if one exists which contains all the bnodes in the graphs being merged.)

> And by the definitions in Section "Notation and terminology", a surface syntax can only serialise scopoed graph, so a surface syntax cannot serialise the merge.

Of course it can. The very act of making the merge as a graph document creates the scope. Every actual RDF document or datastructure defines a scope, and the triples in it comprise a scoped graph. 

> 
> Should I really spend all of my time writing down counter arguments? Don't you (or anyone) see that there *is* a problem with the proposed design?

No. There is no problem with this design, other than your stubbornness in refusing to understand basic ideas of how notations work.

Pat

> 
> 
> AZ.
> 
> 
> Le 14/03/2013 18:13, Peter Patel-Schneider a écrit :
>> My understanding of the semantics in the current Semantics document is as
>> follows:
>> 
>> 1/ Any set of triples is an RDF graph.
>> 2/ Combining RDF graphs is done by taking the union of the triples in them.
>> 
>> That's is, as far as the semantics goes.  I don't see any wording anywhere
>> in Semantics to the contrary.
>> 
>> Note that there is no notion of scope here at all, and none of the
>> semantics depends on scoping in any way.  All of the discussion on scoping
>> graphs is irrelevant, and the discussion of complete graphs could/should be
>> rewritten into something like saying that unions are implied by a set of
>> graphs when each graph includes either all or none of the triples in the
>> union that include any particular bnode.
>> 
>> 
>> The Semantics document also discusses bnode scoping, which is not needed in
>> the semantics per se, but is needed in surface syntaxes and implementations
>> that identify bnodes using syntactic elements that can be accidentally
>> repeated.   Here bnode scope is used to determine when using the same
>> syntax (e.g., a bnode identifier) results in the same bnode or results in a
>> different bnode.
>> 
>> Why is this (currently) in Semantics?  Just because it (currently) isn't in
>> Concepts.
>> 
>> 
>> 
>> In my opinion, quite a bit of the discussion of scoping in Semantic need
>> not survive in either Semantic or Concepts, but it might have some
>> explanatory value so I'm not arguing about removing it.
>> 
>> peter
>> 
> 
> -- 
> 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/
> 
> 

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Received on Friday, 15 March 2013 15:37:38 UTC

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