Re: [GRAPH] graph deadlock?

Le 19/12/2011 21:28, Richard Cyganiak a écrit :
> Pat,
>
> On 17 Dec 2011, at 17:21, Pat Hayes wrote:
>>> (1) RDF Datasets. It consists of labelled graphs: (G, l), where l
>>> is an URI. (Some raised the possibility to use literals for 'l',
>>> but I think there is a consensus to use URI-s). There is no
>>> semantic relationship between 'G' and 'l', so something like
>>> (with an ad-hoc syntax here):
>>>
>>> ( {a:b c:d e:f}, mailto:ivan@w3.org }
>>>
>>> is a perfectly o.k. labelled graph in an RDF Dataset
>>
>> Fine so far, but we get into a problem when we do the details. I
>> personally have no problem (well, a kind of private horror, but
>> thats just me) with datasets as you describe them here. The problem
>> is, people apparently want to both have these AND use the URIs in
>> them to refer to the associated graph in RDF triples (eg in
>> 'metadata' graphs.) And that combination is simply illegal,
>> according to the 2004 RDF specs.
>
> You keep saying things like that.
>
> I keep asking for quotations from the specs that back up these
> claims.
>
> You never deliver, or deliver only a vague pseudo-arguments that rely
> on unstated assumptions not required by the specifications.
>
> When you say “this is illegal in RDF” then I think this has to be
> read as “I don't like it”.

In this particular, it's trivial that it does not work. You can't have 
something that RDF-denotes a graph and RDF-denotes something else at the 
same time.

But this is probably irrelevant as a URI does not need to "denote" it 
can simply be "associated with". E.g., ex:me associated with a graph 
*and* denotes me. It's clear that this is causing trouble to people who 
would like the URI to denote the graph, but we have to live with it as, 
apparently, it is common practice.

>> We could simply declare that RDF has no semantics, and is simply to
>> be used by programmers to mess around with in ways they find handy.
>> Really, this might be the best way to move forward. But until we do
>> this, we have to take the semantics seriously.
>
> Or we could just not bother giving any formal semantics to any new
> parts that are added to RDF. Several parts of RDF don't have a formal
> semantics and work pretty much fine anyways, e.g., RDF lists.

Yes we could do that but the reason why I want to have a formal 
semantics is that you can then build on top of it without having to 
redefine the common ground over and over again. It's like RDF: the 
semantics of the RDF vocabulary is very very weak and not quite useful 
at all. But you can build RDFS on top of it, then OWL, with a common 
ground (although OWL DL is departing from this idea).

>
> Best, Richard
>

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Received on Tuesday, 20 December 2011 10:31:06 UTC