W3C home > Mailing lists > Public > public-owl-wg@w3.org > November 2007

Re: ISSUE-67 (reification): REPORTED: use of reification in mapping rules is unwise

From: Ian Horrocks <ian.horrocks@comlab.ox.ac.uk>
Date: Mon, 26 Nov 2007 13:50:15 +0000
Message-Id: <73A21185-0E7E-4AA6-8DB3-DAA21740A0CF@comlab.ox.ac.uk>
Cc: Boris Motik <boris.motik@comlab.ox.ac.uk>, "'OWL Working Group WG'" <public-owl-wg@w3.org>
To: Jeremy Carroll <jjc@hpl.hp.com>

On 21 Nov 2007, at 11:59, Jeremy Carroll wrote:

> Boris Motik wrote:
>> Hello,
>> I don't want to get into an argument here whether this is really  
>> needed or not; however, I wanted to point out that I spoke to quite
>> a few people asking for the annotation of axioms.
> There are always trade offs. I certainly am not trying to suggest  
> that the feature was unmotivated. But *need* is quite a strong word.
> In the wider scheme of things, the Web and Semantic Web are not  
> *needed*, (not in the way that we need bread and water; love and  
> friends) so I am pretty sure that any feature of OWL 1.1 is not  
> necessary either.

Come on Jeremy -- this is a rather silly argument. Of course OWL  
(1.1) and the Semantic Web "don't amount to a hill of beans in this  
crazy mixed up world", but this is hardly pertinent, and I think that  
we all know roughly what is meant in this context by "need". Just to  
make this a little more concrete, it is clear that improving/ 
extending the OWL 1.0 annotation framework (or lack of it) is a key  
requirement for and motivation of OWL 1.1 (see http://www.w3.org/2007/ 
OWL/wiki/Overview). As Alan has already pointed out, this is  
supported by conversations with experienced users representing key  
user groups; for example, one of the main reasons given by the OBO  
community for *not* using OWL is its very weak annotation mechanism.

>> There is yet another solution: we might have axiom annotations in  
>> the structural specification, but then disallow (or simply delete
>> them) when the ontology is exported into OWL RDF.
> Interesting.
> A key raison d'Ítre for the previous WG was to have a single web  
> ontology language, OWL, that encompassed the DL view and the RDF  
> view. To get such interoperability was, in the view of that WG, a  
> very valuable goal.

It was considered a valuable goal, but proved to be impossible to  
fully realise. As you know, a compromise solution was arrived at  
whereby there are two different languages with different semantics.  
For the syntactic intersection of these two languages, it is  
conjectured that the two semantics lead to similar entailments; it is  
known that they do not lead to the *same* entailments. This does not  
seem to have led to any practical difficulties.

> It is always possible for us to give up on that goal, and then  
> perhaps the key task of this WG is merely to squabble over names  
> (i.e. what is OWL?, is it the DL version, or the RDF version?)

The proposed solution is to maintain the status quo -- i.e., to try  
to keep the semantics "aligned" w.r.t. the language intersection, but  
with the understanding that there may need to be some "give" in this  

> More constructively, what I am hearing, I think, is that the  
> requirement is for comments that have no semantics and just fit  
> into the specification in the right way.
> In RDF/XML there has always been the capability to have such  
> comments - they look like:
> <!--
>  This is a comment, it has no bearing on the formal semantics of  
> the document.
> -->
> It may be possible to provide say, an informative GRDDL transform  
> from an XML version of the axioms, to RDF/XML, and back again, that  
> round trips comments appropriately.

As you probably recall, this was discussed and dismissed in the  
WebOnt working group for the reason that it is much too low-level (it  
is a feature of XML), and that such comments may be lost when  
documents are processed. What you propose w.r.t. GRDDL sounds more  
like a hack than a realistic solution. Moreover, this mechanism would  
hardly satisfy the requirement to have a more comprehensive framework  
that allowed (at least) for annotating axioms as well as entities.


> Jeremy
Received on Monday, 26 November 2007 13:50:28 UTC

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