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Re: Semantics for stateful resources

From: Andy Seaborne <andy.seaborne@epimorphics.com>
Date: Mon, 28 May 2012 11:27:51 +0100
Message-ID: <4FC35327.8060502@epimorphics.com>
To: public-rdf-wg@w3.org


On 25/05/12 14:19, Richard Cyganiak wrote:
> Hi Antoine,
>
> I think I get your point about the benefit of having the entailments
> of the individual graphs in some form as entailments of the dataset.
> I am not sure that I like the way it's done in your proposal, because
> it doesn't distinguish between “that what was said” and “that what
> could be inferred from what was said”. I think it's important to keep
> those separate and to be very explicit about the first. So I prefer a
> “quoting” semantics for the named graphs. Perhaps it's possible to
> have both.

Antoine's example:

:year2008 {
  :Joe  :worksFor  :AcmeCorp .
  :worksFor  rdfs:domain  :Employee .
}
==>
:year2008 { :Joe  a  :Employee }

has a particular feature in that entailment depends only on RDFS specs.

Even with the full possibilities of redefining URIs by the contexts 
proposals (not the spaces one), I'm not sure that allowing changing to 
core RDF(S) vocabulary is desirable. The laws of RDF (the specs) should 
be taken as universal and a side effect of that is that vocabulary the 
specs defines is fixed.

With that view, RDF(S) has defined rdfs:domain so by writing

  :Joe  :worksFor  :AcmeCorp .
  :worksFor  rdfs:domain  :Employee .

one is also writing

   :Joe  a  :Employee .

Whether that's inferred from the concrete triples or stated in the 
concrete triples isn't important and can't be relied on.

I don't have a fundamental problem with a system based on quoting 
concrete observed graphs - I just think that some vocabulary is fixed 
because specs are fixed (datatypes, RDF vocabulary) so entailment can 
follow.

	Andy
Received on Monday, 28 May 2012 10:28:25 GMT

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