W3C home > Mailing lists > Public > public-rdf-wg@w3.org > February 2013

Re: Problem with auto-generated fragment IDs for graph names

From: Pat Hayes <phayes@ihmc.us>
Date: Mon, 18 Feb 2013 09:03:25 -0600
Cc: RDF-WG <public-rdf-wg@w3.org>
Message-Id: <BCC66A92-F37C-4BD6-8923-4EDE5DEE72FA@ihmc.us>
To: Andy Seaborne <andy.seaborne@epimorphics.com>

On Feb 17, 2013, at 7:19 AM, Andy Seaborne wrote:

> 
> 
> On 15/02/13 22:17, Pat Hayes wrote:
>> 
>> On Feb 15, 2013, at 1:38 PM, Andy Seaborne wrote:
> ..
>>> 
>>> One simple entailment design would be:
>>> 
>>> {ex:doc1 :author "Bob" }
>>> ex:doc1 {:TheMoon :madeOf :greenCheese }
>>> 
>>> =>
>>> 
>>> {_:x :author "Bob" }
>>> _:x {:TheMoon :madeOf :greenCheese }
>>> 
>> 
>> But that is exactly what would not be valid, using the current
>> semantics (or rather lack of it) for the premises. That first graph does
>> NOT require ex:doc1 to denote the graph {:TheMoon :madeOf :greenCheese
>> }. The URI might denote something entirely different, and the default
>> graph will say that Bill authored that, whatever it happens to be.
>> Whereas (I am suggesting we can impose the condition that) in the second
>> case, the bnode can only denote that graph.
> 
> OK - we're clear then that this is a proposal, and not something that automatically falls out of the current specs.

Of course, since the current specs dont mention bnodes used as graph labels. But it would not require any change to the current specs (ie to the semantics of IRIs or bnodes themselves.)

Right now a dataset is the scope of any bnode in that dataset, so the semantics says that bnodes are like existential variables bound at the edge of the dataset:

(exists (_:x)( <dataset goes here> )

What I am suggesting amounts to treating any blank node graph labelling as being like an equation:

(exists (_:x)( ...._:x....  & _:x = <graph> )

which gives exactly the meaning Im suggesting we should specify. 

(We might want to legislate what happens if the same bnode is used to label several graphs. It could be an error or it could mean we are referring to the union.)

Pat

> 
> 	Andy
> 
> 
>> 
>> Pat
>> 
>> 
>>> 	Andy
>>> 
>>> 
>> 
>> ------------------------------------------------------------
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>> 40 South Alcaniz St.           (850)202 4416   office
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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 Monday, 18 February 2013 15:03:58 GMT

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