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Re: Labelled graphs

From: Andy Seaborne <andy.seaborne@epimorphics.com>
Date: Wed, 25 Apr 2012 13:11:07 +0100
Message-ID: <4F97E9DB.5010908@epimorphics.com>
To: Ivan Herman <ivan@w3.org>
CC: Sandro Hawke <sandro@w3.org>, public-rdf-wg@w3.org


On 25/04/12 12:28, Ivan Herman wrote:
>
> On Apr 25, 2012, at 05:16 , Sandro Hawke wrote:
>
>> On Tue, 2012-04-24 at 16:05 +0100, Andy Seaborne wrote:
>>>
>>> On 24/04/12 13:04, Sandro Hawke wrote:
>>>> (mostly agreement, a few details)
>>>>
>>>> On Tue, 2012-04-24 at 12:03 +0100, Andy Seaborne wrote:
>>>>>
>>>>> On 17/04/12 16:59, Guus Schreiber wrote:
>>>>> ...
>>>>>
>>>>>> An attempt at formulating a possible conclusion/consensus from this thread:
>>>>>>
>>>>>> * Non-typed labels are simply associations, no special semantics
>>>>
>>>> There are some semantics, though: the label IRI (or blank node) denotes
>>>> something (maybe call it a "labeling object"), and that something is
>>>> associated with the graph.
>>>
>>> Given the "something" indirection, whether that counts as "semantics" or
>>> not is a bit moot to me.  It's "no fixed semantics".
>>
>> Here's the part that's important to me:
>>
>>         Under OWL entailment and our dataset semantics, does
>>            {<u1>  owl:sameAs<u2>  }
>>            <u1>  {<a>  <b>  <c>  }
>>         entail
>>            <u2>  {<a>  <b>  <c>  }
>>         ?
>>
>
> FWIW, in the case of http://www.w3.org/2011/rdf-wg/wiki/Graphs_Design_6.1/Sem the answer is clearly yes.

I think this is at a different level.

(I think that) the most basic thing we (this WG) needs to do is define 
syntax so that things do not go wrong.  This does not need to fix the 
semantics for all time.

We have some interesting approaches on top of that (6.1, RDFC etc) 
emerging, and we have identified different use cases 
(rdf:StaticGraphContainer, rdf:Graph).  Prov-WG and eGov-WG may also 
have something to say.

The approaches look interesting but they have not been "field tested". 
If the syntax and collision avoidance is set up right, this WG has 
enabled the further refinements over time beyond the WG timescale.

As to owl:sameAs:

1/ owl:sameAs works well on properties and classes, less well on 
individuals (is your "London" the same as my "London" mine?  For all time?)

2/ Actually as written, the answer to Sandros example is

"yes, same dataset" (iri denotes X, X associated with graph + owlSameAs 
then the <u1> <u2> denote the same X because the assertion in a graph so 
uniform denotation applies).

"no, across datasets" (all bets are off, without further knoweledge 
because two uses of the same <u> may be, say, different views of the 
same StaticGraphContainer. i.e. <u> and <u> labelling may be different, 
different people observed the web at different times.  That's reality. 
Time enters the picture.

	Andy

>
> Ivan
>
> ----
> Ivan Herman, W3C Semantic Web Activity Lead
> Home: http://www.w3.org/People/Ivan/
> mobile: +31-641044153
> FOAF: http://www.ivan-herman.net/foaf.rdf
>
>
>
>
>
Received on Wednesday, 25 April 2012 12:11:41 UTC

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