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Re: proposed reply to Re: OWL S&AS: Translation to RDF Graphs

From: Jeff Heflin <heflin@cse.lehigh.edu>
Date: Thu, 15 May 2003 10:56:18 -0400
Message-ID: <3EC3AA92.B65D40B5@cse.lehigh.edu>
To: Jeremy Carroll <jjc@hpl.hp.com>
CC: www-webont-wg@w3.org

Jeremy Carroll wrote:
> 
> I had some doubt about this response
> 
> >A normative definition of this is very likely to be no more intelligible
> >than the current sitation.  A non-normative and incomplete, but more
> >comprehensible discussion would be useful.  The Guide
> >(http://www.w3.org/TR/owl-guide/ serves as at least a partial vehicle for
> >this purpose

I agree with Jeremy here. I do not believe the response is satisfactory.
I only know of a few people who have ever tried to use S&AS to find out
information about the syntax of OWL, and every time it seems that they
have a similar reaction to Dave Beckett. I believe Jeremy pointed some
of this out when he first reviewed S&AS, and I more recently encountered
this difficulty when trying to understand the syntax of restrictions. I
quote from my message of April 23 [1]:

  Second, although the AS&S makes it easy to transform from the abstract
  syntax to RDF, I think it is much harder to do the reverse
  transformation (which actually seems like a more common one). I think
it
  would be nice to have a table that presents this transformation. This
  may also be useful in placating people who ask "where's the official
  syntax?"

This seems like an issue we can't just sweep under the rug. I think we
need to provide a table that translates from RDF to the abstract syntax
(if it has to be non-normative then so be it). There may be some
complexity in describing the fact that some RDF graphs are disallowed,
but I believe it can be managed. For example, we could do an
allValuesFrom restriction as follows:

_:x rdf:type owl:Restriction . 	| restriction(T(ID)
allValuesFrom(T(range)))
_:x rdf:type owl:Class . [opt]  |
_:x rdf:type rdfs:Class . [opt] |
_:x owl:onProperty ID . 	|
_:x owl:allValuesFrom range . 	|
* no others with subject _:x *  |

Note, the "no others" part is needed to indicate the OWL-Lite/DL
restriction that a Restriction is limited in what properties it may
have. In particular, you can't have allValuesFrom with someValuesFrom,
hasValue, cardinality, etc.

Note, I do not believe that such a table would be design change, so it
wouldn't force us to go through another last call.

I request that we discuss this at the telecon today during the time
alloted to discuss public comments.

Jeff


[1] http://lists.w3.org/Archives/Public/www-webont-wg/2003Apr/0122.html

.
> 
> and later
> 
> >Agreed, but the Guide serves this purpose.
> 
> Two problems with these references to the Guide:
> 1: I think Peter is talking about things that might have been included in the
> Guide rather than things that actually are in the Guide.
> 
> (or maybe it's only the second point)
> 
> 2: I don't think of Dave Beckett as a Guide reader.
>    He's happy reading fairly turgid technical material for developers, and he
> seems to be saying that this section looked too difficult, and seems to be
> asking the fairly open-ended question of can we make it easier?
>   The answer might be no we can't, but I don't think the answer Dave is after
> is found in the Guide.
> 
> Jeremy
Received on Thursday, 15 May 2003 10:56:27 GMT

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