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Re: RDF-ISSUE-98 (graph-dataset-semantics-unified): Should the semantics of RDF graphs and the semantics of RDF datasets be combined into one unified semantics? [RDF Semantics]

From: Antoine Zimmermann <antoine.zimmermann@emse.fr>
Date: Fri, 14 Sep 2012 10:07:35 +0200
Message-ID: <5052E5C7.80008@emse.fr>
To: Pat Hayes <phayes@ihmc.us>
CC: public-rdf-wg@w3.org

Le 14/09/2012 07:53, Pat Hayes a écrit :
> On Sep 13, 2012, at 8:16 AM, Antoine Zimmermann wrote:
>> ISSUE-98 is not trivial.
> I disagree. With your semantics proposal and the equivalence of a
> graph to a dataset with no named graphs, it is entirely trivial to
> unify the semantics. In fact, they are in effect already unified.

Sorry but, I maintain, it's *not* trivial. Of course the dataset 
semantics can interpret graphs alone. It can do this because it relies 
on the RDF semantics. To exist in its current, the semantics of RDF 
graphs must exist on their own.

>> My vote at the moment is for not changing the RDF semantics
>> document beyond simple updates and having a separate document about
>> dataset semantics.
>> If you or Pat, or anyone else, has a proposal to make a unified
>> semantics that does not require rewriting RDF Semantics completely,
>> then please put it in the wiki and let us discuss it.
> I already made this proposal in an earlier email
> (http://lists.w3.org/Archives/Public/public-rdf-wg/2012Sep/0109.html).

No. What you write is exactly the same as what I wrote, in a different 
form. It assumes that RDF semantics is what it currently is, and build 
on top of it.

> It requires no change to RDF semantics for RDF graphs. It would be
> trivial (and natural) to add the dataset semantics as a later section
> to the RDF semantics document (assuming that we adopt this semantics
> for datasets, of course.)

If you don't want a new document, you can always put a new section to 
another one. That does not make the whole thing "unified".

> There seems to be no point in having a
> separate document, given that the semantics document already covers
> simple, RDF-, RDFS- and D-interpretations.

Yes, and it could cover any extension of the RDF semantics, including 
OWL and more. But the dataset semantics is not a semantic extension, in 
the sense used in the document, of the RDF semantics. It's another logic.

> BTW, I have already proposed to greatly shorten the semantics
> document and keep it strictly concerned with describing the model
> theory, as well as eliminating most, if not all, of the elaborate
> completeness proofs and so on. In particular, the various inference
> rules should be put into a different document, as they are not
> immediately concerned with semantics.
> By the way, do you think there might be a complete set ot inference
> rules for database entailment?

You mean dataset entailment, for sure. Dataset entailment does not have 
complete inference rules because it depends on entailment regimes that 
may not have a complete set of inference rules.


> Pat
>> AZ
>> Le 13/09/2012 14:39, Richard Cyganiak a écrit :
>>> On 13 Sep 2012, at 13:12, Andy Seaborne wrote:
>>>> We would have to be careful to explain why we then don't have
>>>> datasets-inside-datasets and "named datasets".
>>> It's a somewhat arbitrary restriction in the abstract syntax
>>> that makes implementations simpler while still allowing the use
>>> cases we care most about to be addressed.
>>>> It's not a block to the idea but keeping them separate does
>>>> make it clearer where the boundary is.
>>> I think that keeping them separate would make the Semantics
>>> document more complicated. The Semantics document is complicated
>>> enough as it is. I think making it more complicated to account
>>> for a syntactic restriction is not a good idea. If writing a
>>> semantics that is more general than necessary for the abstract
>>> syntax turns out to be simpler, then readers are better served by
>>> the simpler thing, IMO.
>>> A related case here is literals-as-subjects, which is a
>>> well-motivated restriction that I never would want to remove, but
>>> I'd prefer if the Semantics document would use a generalized
>>> notion of RDF graphs that doesn't have the restriction, because
>>> that would remove probably a page of pointless and
>>> hard-to-understand trickery that is needed to work around the
>>> restriction. At least I personally found that a barrier to
>>> understanding the document.
>>> Best, Richard
>> -- Antoine Zimmermann ISCOD / LSTI - Institut Henri Fayol École
>> Nationale Supérieure des Mines de Saint-Étienne 158 cours Fauriel
>> 42023 Saint-Étienne Cedex 2 France Tél:+33(0)4 77 42 66 03
>> Fax:+33(0)4 77 42 66 66 http://zimmer.aprilfoolsreview.com/
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Antoine Zimmermann
ISCOD / LSTI - Institut Henri Fayol
École Nationale Supérieure des Mines de Saint-Étienne
158 cours Fauriel
42023 Saint-Étienne Cedex 2
Tél:+33(0)4 77 42 83 36
Fax:+33(0)4 77 42 66 66
Received on Friday, 14 September 2012 08:07:51 UTC

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