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Re: RDF Semantics review: RDFS interpretations

From: <herman.ter.horst@philips.com>
Date: Fri, 21 Feb 2003 17:34:32 +0100
To: Dan Connolly <connolly@w3.org>
Cc: www-webont-wg@w3.org, Pat Hayes <phayes@ai.uwf.edu>
Message-ID: <OFA9EFF1E9.BDD587F9-ON41256CD4.0059E568-C1256CD4.005B37E4@diamond.philips.com>

> On Thu, 2003-02-13 at 05:03, herman.ter.horst@philips.com wrote:
> > > On Thu, 2003-02-06 at 13:05, herman.ter.horst@philips.com wrote:
> > > > RDF Semantics, version of 23 January 2003
> > > 

[...]

> 
> [...]
> > > > The semantic conditions on rdfs:range and rdfs:domain
> > > > do not yet incorporate an explicit domain assumption as just
> > > > discussed.  It seems that additions such as the following need 
> > > > to be made:
> > > > 
> > > > If <x,y> is in IEXT(I(rdfs:range)) 
> > > > [then x is in IP and y is in IC] and 
> > > > [if, in addition,] <u,v> is in IEXT(x) then 
> > > > v is in ICEXT(y)
> > > > 
> > > > If <x,y> is in IEXT(I(rdfs:range)) 
> > > > [then x is in IP and y is in IC] and 
> > > > [if, in addition,] <u,v> is in IEXT(x) then 
> > > > u is in ICEXT(y)
> > > 
> > > That seems substantive, but I'm not sure I understand
> > > the problem. Could you state it as an entailment test,
> > > please?
> > 
> > (There is a typo in the second item: it should be domain instead
> > of range.)
> > 
> > These are omissions, which seem to be a remnant from the April 2002 
> > version of the RDF MT, where the IEXT had all of IR as a domain.
> > In the current version, something needs to be added.
> > You cannot speak of IEXT(x) unless you assume that
> > x is in IP.
> > In both Peter's and my reading of the text, there should
> > be the additions "then x is in IP" and "if, in addition",
> > in both items.
> > In "my interpretation" of IC/ICEXT, the assumptions
> > "y is in IC" should also be added to both items.
> > 
> > So here the Last Call text has an inappropriate omission 
> > of a mathematical detail (a small error).
> > I cannot relate this to entailment tests.
> 
> Hmm... maybe if I explain a bit?
> 
> An entailment test is just a very simple
>                if P then Q
> theorem. If there's a bug in the RDF semantics,
> then we should be able to exhibit some
> "if P then Q" theorem that, by design,
> holds, but by the spec as witten, does
> not hold... or vice versa... or at least:
> where the answer to whether it holds or
> not isn't sufficiently clear.
> 
> It's vitally important that substantive
> technical issues get captured in this form.
> It's just about the only reliable way to make sure
> the deployed code matches the disposition
> of the issue.
> 
> It also greatly facilitates group-to-group
> communication. These tests leave very little
> room for misunderstanding, matters of
> taste/style, etc.
> 
> If there is no way to make this issue observable
> as an entailment test, then I don't believe
> it's a substantive issue.
> 
> -- 
> Dan Connolly, W3C http://www.w3.org/People/Connolly/
> 
> 
> 

Thank you for this explanation.
I have used this explanation to formulate an entailment test
for another point that I raised about the RDF Semantics
document [1].

The issue above deals with the mathematical correctness of 
the statement of a certain condition in de RDFS semantics, 
and I still feel that this seems to be beyond entailment tests.
I have tried to make the point clearer in my mail to 
rdf-comments [2].

Herman ter Horst

[1] http://lists.w3.org/Archives/Public/www-rdf-comments/2003JanMar/0354.html
[2] http://lists.w3.org/Archives/Public/www-rdf-comments/2003JanMar/0350.html
Received on Friday, 21 February 2003 11:36:29 GMT

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