- From: Pierre-Antoine Champin <pierre-antoine.champin@liris.cnrs.fr>
- Date: Tue, 04 Oct 2011 22:48:28 +0200
- To: Richard Cyganiak <richard@cyganiak.de>
- CC: "public-rdf-wg@w3.org" <public-rdf-wg@w3.org>
Richard, On 10/04/2011 05:08 PM, Richard Cyganiak wrote: > On 2 Oct 2011, at 18:06, Pierre-Antoine Champin wrote: >> As you stress it, RDF does not dictate which IRI should denote >> which resource (including graphs). I don't think I ever suggested >> to change that. >> >> However, RDF dictates that each time I use the same IRI (as a >> node), it denotes the same resource. > > No, it doesn't. > > RDF Semantics is concerned with the interpretation of *individual RDF > graphs*. Well, that's what I meant. > As far as RDF Semantics is concerned, the same IRI may identify > completely different things in different RDF graphs. > > It is the social contracts and conventions of the web that encourage > us to converge on a single unique referent for each IRI. This is > orthogonal > > For example, in this triple: > > <#me> foaf:homepage <http://richard.cyganiak.de/>. > > we all know what the subject of the encoded statement is. But that's > not because of RDF Semantics. As far as RDF Semantics is concerned, > <http://richard.cyganiak.de/> denotes a completely arbitrary > resource. It's conventions that allow us – and the software we create > – to understand that the target is a web page that can be accessed > via a browser and so on. > > This mechanism *works*. 200% agreed. > I suggest to treat graph names in exactly the same way. It depends how you define "the same way". IRIs currently must be used consistently inside a single graph. I was assuming that this principle would extend to datasets, should we define them in the RDF spec. >From your response to my messages and Pat's, I now understand that you do not want to go that far. > When we assert inside some RDF dataset: > > <#me> ex:assertsGraph <#graph1>. > > then as far as RDF Semantics is concerned, <#graph1> denotes an > arbitrary resource. It's conventions – and the definition of > ex:assertsGraph – that allow us, and our software, to understand that > this talks about a different graph within the same dataset. > > When you and Pat demand that the denotation of graph names in RDF > datasets be fixed to the graph, then you conveniently ignore the fact > that RDF Semantics currently doesn't have the power to fix the > denotation of *anything* (except the RDF(S) built-ins), and all literal values... > and *always* > defers to convention for establishing the connection between IRIs and > things. RDF works nevertheless. Why should it be any different for > graphs? Well, if graphs in a dataset are g-snap, then they look very much like literals to me, and I would tend to read <some-uri> { :a :b :c } as something like <some-uri> owl:equals " :a :b :c . "^^rdf:turtle (if I may indulge in my former proposal...). In that case, it does indeedfix the semantics of <some-uri>, but not more than <the-answer> owl:equals 42 . does. This already works in RDF (well OWL-full...). Now, if graphs are g-boxes, I would rather read <some-uri> { :a :b :c } as something like <some-uri> rdf:hasCurrentGSnap [ log:implies " :a :b :c . "^^rdf:turtle ] where rdf:hasCurrentGSnap would have rdf:GBox as its domain, so I can *at least* infer that <some-uri> denotes *some* g-box. In any case, I do not see how what I propose implies something radically different from the kind of inference that already exist in RDF. Let's discuss this tomorrow. pa > > Best, Richard
Received on Tuesday, 4 October 2011 20:49:04 UTC