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Re: [Graphs] Fwd: Comments on "SPARQL 1.1 Uniform HTTP Protocol for Managing RDF Graphs"

From: Nathan <nathan@webr3.org>
Date: Fri, 18 Mar 2011 16:25:32 +0000
Message-ID: <4D83877C.9040508@webr3.org>
To: Pat Hayes <phayes@ihmc.us>
CC: RDF Working Group <public-rdf-wg@w3.org>
Hi Pat,

Pat Hayes wrote:
> a. RDF graphs are abstractions, which are not information resources. (Think parse trees rather than documents.)
> b. RDF g-boxes are information resources, which can be identified by a URI in the usual Web way. A 'named graph' is actually a named g-box. An RDF dataset is a collection of named g-boxes. (If we agree on this, we should ask DAWG to make this clear and we must provide them with a stable vocabulary that they can use to make it clear. Or we will have to use their stable vocabulary.) 
> c. "RDF document" can mean either a g-box or a g-text, in much the same way that an HTML file, suitably located on a server, can be seen as an information resource, but a copy of it can also be seen as a REST-representation of that resource. So to answer Kjetil: yes, a URI can identify an RDF document, but not an RDF graph. But it can also identify a resource which emits different RDF documents  from time to time. 

g-box

> d. We endorse http-range-14, so a 'named graph' must be a named g-box, if the naming URI  returns a 200-level HTTP response to a GET request.

+1 from me up till here.

> If someone wants to name an actual RDF graph with a bare URI, they have to use 303 redirection and somehow indicate that it is the actual abstract graph, rather than the g-box, that they wish to name. I really don't know how to do this indicating.

the notion of a fixed g-box, one which always produces a g-text encoding 
the same g-snap could be of use here, that way any statements made about 
the contents of the g-text (how many triples it serializes etc) should 
remain consistent over time, however..

> Maybe it could be done by using a graph literal and owl:sameAs, for example (??That seems to me to be overkill, in that if you already have the entire graph in the literal, why bother referring to some other version of it using a name?) Or maybe we should provide some reserved vocabulary to say this directly in the RDF itself. Whatever, but we do need to specify some way to do it.

This is precisely the usecase I've been suggesting "quoted graphs" for

   { triples in here } a :RDFGraph ;
     :source_uri "http://..." .

That way you can talk about the "RDF Graph" without talking about the 
content+meta/representation, for instance it wouldn't have a Content-Type.

Best,

Nathan
Received on Friday, 18 March 2011 16:26:52 GMT

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