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Re: Are you planning to use the Dataset Semantics?

From: Pat Hayes <phayes@ihmc.us>
Date: Tue, 25 Sep 2012 23:59:08 -0500
Cc: W3C RDF WG <public-rdf-wg@w3.org>
Message-Id: <2F88BD01-B9B0-4846-8E05-06BA7B951512@ihmc.us>
To: Sandro Hawke <sandro@w3.org>

On Sep 25, 2012, at 9:25 PM, Sandro Hawke wrote:

> On 09/25/2012 09:54 PM, Pat Hayes wrote:
>> On Sep 25, 2012, at 5:16 PM, Sandro Hawke wrote:
>> 
>> 
>>> For myself, at this point I'm 70% convinced that I can implement all the dataset use cases I understand (the ones I enumerated in the Federated Phonebook examples, plus SPARQL dump/restore) without any standard dataset semantics beyond having a standard place for metadata (eg the default graph in trig and the service description graph in SPARQL).
>>> 
>> Sandro, how can you use metadata *at all* without some way to force a URI to denote a graph? When you use the URI in the metadata RDF, what (semantic or even pragmatic) constraint ensures that what it denotes there is the graph that you have in mind? Or indeed, that it is a graph at all?
>> 
> 
> My current theory is that I can do it via the documentation of the predicate(s) I use with that URI.  

Hmm. But the semantics being discussed right now explicitly distinguishes the graph "named" by the URI it is attached to in a dataset, from the entity the URI is understood to denote. And the RDF semantics says that when a URI is used in an RDF triple, it refers to what it denotes. So your documentation seems, on the face of things, to be at odds with what the semantics says.

The basic point is, you can specify what your property means, but you don't get free rein to say what the graph "name" URI refers to. (At least, not unless you have something like a context to put it in, where you *could* say what it means.) 

Pat


>  Given the emerging sense of what datasets are, I think I can write that document in such a way that it will be quite clear to human readers (and thus the software they write) how it connects to the triples in the named graphs.
> 
> I'm hoping the WG will end up making it really easy to write that documentation, but I'm pretty sure it's possible anyway.
> 
> The example I used in [1] was:
> 
>     <g1> eg:sendCorrectionsTo <mailto:sandro@w3.org
> >.
>     <g1> { w3c:group35462 rdfs:label "SPARQL Working Group" }.
>     <g2> eg:sendCorrectionsTo <mailto:
> ivan@w3.org
> >.
>     <g2> { w3c:group44350 rdfs:label "RDFa Working Group" }.
> 
> (I'm using the default graph for metadata, and leaving off the braces around default-graph triples)
> 
> And then I proposed documenting eg:sendCorrectionsTo something like this:
> 
>     X eg:sendCorrectionsTo Y
> 
>         Note: only meaningful as metadata for a dataset which has a named graph
>         with the name X.
> 
>         Meaning: Y is a good email address for sending corrections to
>         the information in the named graph X.
> 
> 
> This definition doesn't really care whether named graphs are g-boxes or g-snaps, but I think it's probably good enough to work in practice.   Other predicates might be much more precise, of course.   
> 
> I'm not thrilled with the predicate being only meaningful when used in a dataset metadata [I prefered my framing as rdf-spaces] but this works, too, I think.
> 
>         -- Sandro
> 
> [1] http://lists.w3.org/Archives/Public/public-rdf-wg/2012Sep/0181.html
> 
>> Pat
>> 
>> 
>>>    -- Sandro
>>> 
>>> [1] 
>>> http://www.w3.org/2005/10/Process-20051014/tr#cfr
>>> 
>>> 
>>> 
>>> 
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>> 
>> 
>> 
>> 
>> 
>> 
>> 
>> 
> 

------------------------------------------------------------
IHMC                                     (850)434 8903 or (650)494 3973   
40 South Alcaniz St.           (850)202 4416   office
Pensacola                            (850)202 4440   fax
FL 32502                              (850)291 0667   mobile
phayesAT-SIGNihmc.us       http://www.ihmc.us/users/phayes
Received on Wednesday, 26 September 2012 04:59:39 GMT

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