W3C home > Mailing lists > Public > semantic-web@w3.org > July 2012

Re: OWL equivalentClass question

From: David Booth <david@dbooth.org>
Date: Fri, 13 Jul 2012 13:47:01 -0400
To: Alan Ruttenberg <alanruttenberg@gmail.com>
Cc: Michael Schneider <schneid@fzi.de>, semantic-web@w3.org, nathan@webr3.org
Message-ID: <1342201621.3555.32382.camel@dbooth-laptop>
On Fri, 2012-07-13 at 13:08 -0400, Alan Ruttenberg wrote:
> 
> 
> On Fri, Jul 13, 2012 at 10:30 AM, David Booth <david@dbooth.org>
> wrote:
>         On Fri, 2012-07-13 at 15:05 +0200, Michael Schneider wrote:
>         > [Hrmph, I found another error in my first post. So forget
>         > all my previous posts, here is complete rewrite with the
>         > errors being fixed.]
>         >
>         > Hi Nathan!
>         >
>         > In the context of datatypes and data ranges (including
>         > datatype restrictions, as you use them in your examples),
>         > the term "owl:equivalentClass" is used in the RDF syntax
>         > of OWL 2 for stating /datatype definitions/; see [1] for
>         > the specification of datatype definitions, and Table 16
>         > in [2] for the reverse RDF mapping from the RDF encoding
>         > of datatype definitions to their OWL 2 functional syntax
>         > counterparts.
>         >
>         > Further, from the last entry of Table 12 in [2], you can
>         > see that the RDF encoding of /datatype restrictions/ is
>         > only defined for blank nodes (as in your first example),
>         > so the mapping of datatype definitions does not apply if
>         > a URI is used instead (as in your second example).
>         
>         
>         So if the blank nodes are skolemized,
>         http://dvcs.w3.org/hg/rdf/raw-file/default/rdf-concepts/index.html#section-skolemization
>         then the OWL 2 mapping breaks?  This sounds like a bug in the
>         mapping algorithm.
> 
> 
> That would be a bug in the skolemization spec, if there is a bug. The
> idea is that new stuff is considered a bug if it breaks old stuff, not
> the other way around.

But that would render skolemization impossible, and it would conflict
with the treatment of blank nodes as existentially qualified variables
http://www.w3.org/TR/rdf-mt/#unlabel
since it would be like saying "there exists an x, but you're not allowed
to name x with a URI".
> 

-- 
David Booth, Ph.D.
http://dbooth.org/

Opinions expressed herein are those of the author and do not necessarily
reflect those of his employer.
Received on Friday, 13 July 2012 17:47:31 UTC

This archive was generated by hypermail 2.3.1 : Tuesday, 1 March 2016 07:42:35 UTC