W3C home > Mailing lists > Public > public-rdf-wg@w3.org > February 2012

Re: Islands (ACTION-148)

From: Pat Hayes <phayes@ihmc.us>
Date: Tue, 28 Feb 2012 21:51:55 -0600
Cc: public-rdf-wg@w3.org
Message-Id: <6CC18DA8-7AAB-436A-831C-CF8B8A179DF3@ihmc.us>
To: Antoine Zimmermann <antoine.zimmermann@emse.fr>

On Feb 28, 2012, at 11:39 AM, Antoine Zimmermann wrote:

> ....
>> If I put two copies of a graph into a single trig document with two
>> different lables, one of the copies does not entail the other, even
>> though they are the same graph.
> 
> Again, no, the RDF graphs entail each others. It's the pairs (n1,g), (n2,g) that do not entail each others. Which is exactly what I would like to have. Otherwise, I would not have made two copies in the first place.

So the added label *changes the meaning* of the graph it is attached to. (It must do so, since otherwise the graph must entail itself, trivially.) So, the natural question to ask is, how does the meaning change? That is, where in the semantics of these graph/name pairs, is there something that makes it mean something different from what the bare graph would mean? One wants to see a specification of an interpretation structure (like the INT/EXT mappings in the RDF semantics, but probably involving the labels in some way) which assigns meanings to the basic symbols, and then precisely given truth conditions which specify, given such a structure, what the larger syntactic objects - triples, graphs, named graphs and datasets - mean in that structure. So far I dont see that in your proposal. 

BTW, after a brief attempt to actually do it this way, I think it is possible to rewrite your semantics in such a way that it is formally equivalent to the quad-based semantics I proposed. Which is encouraging, I guess. However, it does mean that *every* triple in *every* named graph has to be understood in the 'quad' way, which is rather a lot to swallow. And it depends on being able to use a graph label in many different datasets with the same meaning, so the scope of these labels has to be very wide; and it does not have the label URIs denoting the graph they name (unlike N3, for example, and ruling out Sandro's interpretation as meta-data.) 

Pat

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Received on Wednesday, 29 February 2012 03:52:27 UTC

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