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Re: Draft for a "minimal dataset semantics"

From: Antoine Zimmermann <antoine.zimmermann@emse.fr>
Date: Thu, 13 Sep 2012 18:50:43 +0200
Message-ID: <50520EE3.9010002@emse.fr>
To: "Peter F. Patel-Schneider" <pfpschneider@gmail.com>
CC: RDF WG <public-rdf-wg@w3.org>
Le 13/09/2012 03:08, Peter F. Patel-Schneider a écrit :
> I don't think that example 2.16 is correct.

I'm afraid you're right.


> It seems to me that any dataset with a consistent default graph is
> consistent.

I consider this to be good news.


> Any interpretation of the default graph can be extended to an
> interpretation of the dataset by mapping every resource to inconsistent
> graphs.   This trivially satisfies "IGEXT(/I_d /(/n/)) is defined and
> /E/-entails g" as an inconsistent graph entails every graph.

Correct. So there must be at least 2 of the graphs in the graph 
extensions of :n, :m and :o that are inconsistent, but it's not possible 
to know which ones.

Here is another test case:

{ :n  owl:sameAs  :m }
:n { :s  :p  :o }
:m { :x  owl:differentFrom  :x }

OWL-dataset-entails:

:n { :t  owl:sameAs  rdf:type }


> I don't think that this means that 2.16 is not tricky.  There is some
> interaction.  However, this means that named graphs are not independent
> from each other.  In fact, there is a much easier situation showing that
> named graphs are not independent, namely 2.13 T11.2  Similarly, it means
> that named graphs are not independent from the default graph.
>
> It is also the case that an inconsistent default graph makes the named
> graphs irrelevant.

It makes the dataset inconsistent, which is fortunate.


> This last is, I think, a particularly strong point against providing
> this sort of semantics at all.

By "this last", what do you mean? This last test case (T14.1) or this 
last sentence that you wrote above?

I think you mean the former (if it's the latter, I don't see why). Do 
you think that, if the graphs--named and default--were independent, it 
would be acceptable?  That's the alternative proposal where IGEXT maps 
IRIs to graphs, instead of resources to graphs.

But even with IGEXT mapping resources, I find the test case to be even 
more satisfying if it's consistent. It makes it easy to implement a 
reasoner in that case. Take a reasoner for entailment regime E.
Check if any two of the graph IRIs denote the same thing in the default 
graph. For each group of owl:same graph IRIs, reason on the merge of the 
graphs in the group, using the E-reasoner.


AZ

>
>
> peter
>
>


-- 
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 83 36
Fax:+33(0)4 77 42 66 66
http://zimmer.aprilfoolsreview.com/
Received on Thursday, 13 September 2012 16:50:34 GMT

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