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Re: different Semantics proposals (Re: Agenda for 19 Sep 2012)

From: Peter F. Patel-Schneider <pfpschneider@gmail.com>
Date: Tue, 18 Sep 2012 09:05:56 -0400
Message-ID: <505871B4.4060608@gmail.com>
To: Sandro Hawke <sandro@w3.org>
CC: David Wood <david@3roundstones.com>, "public-rdf-wg@w3.org Group WG" <public-rdf-wg@w3.org>

On 09/17/2012 04:46 PM, Sandro Hawke wrote:
> On 09/17/2012 02:02 PM, Peter F. Patel-Schneider wrote:
>
[...]
>
> Can you be a little more specific, and tell a story about something specific 
> someone is likely to want to do that they could do with your proposed 
> semantics and not with the proposal on the agenda?
>
> (The two things I see are: (1) the default graph being "asserted", which 
> seems easy enough to work around if desired [just use a named graph], and 
> (2) URIs being interpreted the same way throughout the dataset... but I 
> can't see what harm that could cause.   Maybe I'm on the wrong track.  Okay, 
> I'm also concerned about unwanted-but-valid inference being done, but that's 
> an issue throughout RDF, not just about datasets.)
>
>       -- Sandro
>

(2) I don't know where in the minimal semantics there is a notion that IRIs 
have to be interpreted the same way throughout the dataset, so I don't see any 
difference here.  If, however, there is a need to interpret IRIs the same way 
throughout a dataset then this would indeed be a vast difference, essentially 
requiring rigid designators in datasets.   This would mean that any equality 
assertion in the default graph would carry over into the named graphs (and 
maybe vice versa).

(1) Even if you used an empty default graph, you get some carry-over into the 
named graphs.   For example, the named graph resources can only be taken from 
the resources in this interpretation. Fortunately (or unfortunately) all RDF 
interpretations are infinite, so there probably are no observable consequences.

But in any case, why should I be forced into turning my default graph into a 
named graph (with some arbitrary name) and adding an empty default graph?


One interesting use of RDF datasets is to collect information from the web.   
The named graphs record the source of the graphs and their contents.  The 
default graph can either be related to these collected graphs or unrelated to 
them.  Having the default graph affect the meaning of the named graphs is 
undesired.

peter
Received on Tuesday, 18 September 2012 13:06:29 GMT

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