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Re: dataset semantics

From: Pat Hayes <phayes@ihmc.us>
Date: Mon, 19 Dec 2011 17:12:47 -0600
Cc: public-rdf-wg@w3.org
Message-Id: <BF7E94AD-E213-4E37-A95C-CA634E8CD476@ihmc.us>
To: Antoine Zimmermann <antoine.zimmermann@emse.fr>

On Dec 19, 2011, at 4:33 AM, Antoine Zimmermann wrote:

> Le 17/12/2011 17:02, Pat Hayes a écrit :
>> 
>> On Dec 17, 2011, at 7:09 AM, Sandro Hawke wrote:
>> 
>>> On Sat, 2011-12-17 at 10:29 +0000, William Waites wrote:
>>>> On Sat, 17 Dec 2011 00:43:38 -0500, Sandro Hawke<sandro@w3.org>
>>>> said:
>>>> 
>>>> sandro>  We haven't quite figured that out yet.  I'm proposing
>>>> one sandro>  part of that is that a dataset being true implies
>>>> its sandro>  default graph is true.
>> 
>>> In terms of an entailment test:
>>> 
>>> <a>   {<b>  <c>  <d>  }
>>> 
>>> does NOT entail
>>> 
>>> {<b>  <c>  <d>  }
>>> 
>> 
>> 
>> Really?? Is this generally accepted, or is it your own conclusion?
>> Because this has the (to me surprising) consequence that publishing a
>> dataset does not assert ANY of the named graphs in it. Which leaves
>> me wondering what the point of having datasets can possibly be in the
>> first place. Does the Semantic Web consist mostly of unasserted
>> fiction?
> 
> As I hope people won't be publishing datasets, there really isn't any problem with this. Really, we have to preserve the triple format as the standard way of publishing data on the Web. Datasets should only be an exchange format and data model for systems that manage data.

I guess I fail to follow this distinction. Isnt the very idea of the semantic web to put, and manage, data on the Web? So if these systems that manage data are functioning within the semantic web, how is that case distinguished from the other case? 

> different sources, and go for N-Quints and define Dataset-sets and reiterate all the hard work of this WG later.

Again I have trouble understanding this. Why would we need to reiterate this if datasets were published? 

There seems to be a background assumption here, which I may just not fully understand, about the reasons why datasets use quads having to do with RDF coming from different sources, and the need to keep these sources distinct. Is that right? Is this the primary reason for considering datasets in the first place, to provide a way to keep track of 'provenance' of RDF graphs, rather than simply merge them into one large graph? If so, we should get this clear and agree on it. So far in these emails I have seen a whole variety of purposes suggested for quadstores/datasets.

> Once you acknowledge this, you understand that the "named" graphs inside the datasets are just saying "there is an RDF graph containing those triples, it is labelled with this 'name' and we don't care whether it is asserted or not". Do we care whether a relational table is "asserting" something in a database?

Actually, i dont really care whether it is asserted or not, but I wanted to establish that it did actually mean something to say that it is asserted. In answer to your rhetorical question, though: yes, of course we care. That is, anyone who plans to use the data had better care, so it had better be clear when a relational table is being asserted as opposed, say, to being just held up for ridicule. 

Pat

> 
>> 
>> Pat
>> 
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>> 
>> 
>> 
>> 
>> 
>> 
>> 
> 
> -- 
> Antoine Zimmermann
> ISCOD / LSTI - Institut Henri Fayol
> École Nationale Supérieure des Mines de Saint-Étienne
> 158 cours Fauriel
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> France
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> 
> 

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Received on Monday, 19 December 2011 23:13:33 GMT

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