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Re: [All] Proposal: RDF Graph Identification

From: Pat Hayes <phayes@ihmc.us>
Date: Thu, 16 Aug 2012 16:23:56 -0500
Cc: public-rdf-wg@w3.org
Message-Id: <F76F03CE-E6AE-4A4E-9263-4FEB9F319C4A@ihmc.us>
To: Sandro Hawke <sandro@w3.org>, "Peter F. Patel-Schneider" <pfpschneider@gmail.com>

On Aug 16, 2012, at 2:58 PM, Sandro Hawke wrote:

> On 08/16/2012 02:18 PM, Peter F. Patel-Schneider wrote:
>> 
>> On 08/16/2012 02:12 PM, Pat Hayes wrote:
>> 
>> [...]
>>> As we tried to make clear in the document: the 'essence' of the proposal is what you just said and what we tried to put there, ie, that "the semantics of an RDF dataset is just the semantics of its default graph" (by default). If the formal, mathematics part is wrong and if it would lead to too much complications to to get it right then, by all means, I am *personally* happy to just nuke it.
>>>> Right, the point is the stuff in 3.1. How that may be expressed is currently eluding me, but Peter you can help here.  We need you for that.
>>> The semantics of a dataset is that of the default graph PLUS the fixing of the denotations of the graph names. That second part is important.
>>> 
>>> Pat
>>> 
>>> 
>> I don't see what is important in this second part at all.  Does it have any interesting consequences, for example?
> 
> Perhaps Pat understand what you're asking and can answer in a way that clears this up.   For my part, well, it seems like these two datasets are different:
> 
> d1:   <g> { <a> <b> 1 }
> 
> d2:  <g> { <a> <b> 2 }
> 

Yes, nice example. To my mind (and I believe with the formal sematnics as currently stated), these two together are a contradiction. There is no interpretation which satisfies them both. 

Pat

> Presumably there are times when I might store/transmit d1, and it would break things if instead I stored/transmitted d2.   So a difference, even if it's not in the default graph, can still make a difference.   Thus the name-graph pairs in a dataset do have *some* semantics.
> 
>     -- Sandro
> 
> 
> 
> 

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Received on Thursday, 16 August 2012 21:24:27 UTC

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