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

From: Sandro Hawke <sandro@w3.org>
Date: Tue, 18 Sep 2012 09:12:26 -0400
Message-ID: <5058733A.2090100@w3.org>
To: "Peter F. Patel-Schneider" <pfpschneider@gmail.com>
CC: David Wood <david@3roundstones.com>, "public-rdf-wg@w3.org Group WG" <public-rdf-wg@w3.org>
On 09/18/2012 09:05 AM, Peter F. Patel-Schneider wrote:
>
> 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).
>

Sorry, I just meant the IRIs of the named graphs, the n's in the <n,g> 
pairs, being interpreted the same as IRIs the default graph.


> (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.
>

I don't see how you can usefully communicate collected information like 
that unless you have a private protocol arranged (in which case this is 
all moot), or you use the default graph for metadata.

        -- Sandro

> peter
>
>
Received on Tuesday, 18 September 2012 13:12:44 GMT

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