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Re: Are you planning to use the Dataset Semantics?

From: Sandro Hawke <sandro@w3.org>
Date: Tue, 25 Sep 2012 22:25:50 -0400
Message-ID: <506267AE.4090705@w3.org>
To: Pat Hayes <phayes@ihmc.us>
CC: W3C RDF WG <public-rdf-wg@w3.org>
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.    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  <mailto:sandro@w3.org?Subject=Re%3A%20different%20Semantics%20proposals%20%28Re%3A%20Agenda%20for%2019%20Sep%202012%29&In-Reply-To=%253C5058B36E.90304%40w3.org%253E&References=%253C5058B36E.90304%40w3.org%253E>>.
     <g1> { w3c:group35462 rdfs:label "SPARQL Working Group" }.
     <g2> eg:sendCorrectionsTo <mailto:ivan@w3.org  <mailto:ivan@w3.org?Subject=Re%3A%20different%20Semantics%20proposals%20%28Re%3A%20Agenda%20for%2019%20Sep%202012%29&In-Reply-To=%253C5058B36E.90304%40w3.org%253E&References=%253C5058B36E.90304%40w3.org%253E>>.
     <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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Received on Wednesday, 26 September 2012 02:25:58 GMT

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