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Re: Graphs, some quick comments

From: Nathan <nathan@webr3.org>
Date: Fri, 22 Apr 2011 00:01:25 +0100
Message-ID: <4DB0B745.2010903@webr3.org>
To: Peter Frederick Patel-Schneider <pfps@research.bell-labs.com>
CC: public-rdf-wg@w3.org
Hi Peter,

I agree and hope the same thing, however I would suggest that the 
semantics and concepts were defined to match the syntactical 
restrictions of the serialization, rather than there being limitations 
on the (or a) conceptual model of RDF.

When I look at other sem web RDFy technologies and libraries, things 
like SPARQL or OWL or libraries like Jena, I find notions of these 
generalized unconstrained triples in many places, just what are they, 
why don't the RDF specifications cater for them, even if it still keeps 
the syntactic restrictions on the RDF serializations.

Surely, at some point, behind the interface, people have seen a literal 
end up in the subject position, or a blank node in the predicate 
position. Heck literal is even a subclass of resource anyway (as DanC 
and Patrick Stickler discussed many moons ago [1]) so it's supported in 
their somewhere, just in a hidden way, that people use behind the 
interface but can't be allowed in to the syntax (from what I can tell).



[1] http://lists.w3.org/Archives/Public/w3c-rdfcore-wg/2002Mar/0098.html

Peter Frederick Patel-Schneider wrote:
> I don't think that this is correct.
> In my opinion RDF and RDFS is defined/constrained by its semantics, or
> at least it should be!  In the RDF Semantics you find the bulk of the
> technical details, and in RDF Concepts you find definitions of many of
> the basic concepts of RDF, mostly in Section 6.
> Yes, RDF/XML, the only official exchange syntax for RDF, is not a
> complete syntax for RDF graphs, but that is really a minor point.
> The stuff you mention below is not (yet?) a part of RDF.
> peter
> From: Nathan <nathan@webr3.org>
> Subject: Graphs, some quick comments
> Date: Thu, 21 Apr 2011 10:52:52 -0500
>> (just dropped these in #swig, copying here)
>> RDF is defined/constrained by it's serializations currently, so anything 
>> in the model/abstract is in the serializations, so when we discuss 
>> things like multiple graphs, graph literals, named graphs, it's done in 
>> terms of syntax, when really there is hardly ever a case where you need 
>> multiple graphs in the syntax, other than when dumping stores or sets of 
>> data, and that ain't RDF.
>> however, behind the interface you need this stuff all the time, but not 
>> over the wire, and RDF doesn't handle that.
>> so, perhaps a higher problem is: RDF is defined in terms of on the wire 
>> needs, but RDF is used as a data model for working with data behind the 
>> interface, and the two have different requirements.
>> if you look at the RDF Graph usecases on the wiki, you'll notice that 
>> most of them are about managing or working with data, and people are 
>> using the syntax of trig or quads to say what they mean - but only the 
>> dumping stores cases actually /require/ having anything in the 
>> serialization.
>> Best,
>> Nathan
Received on Thursday, 21 April 2011 23:02:28 UTC

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