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Re: A slight issue with datatypes in OWL 2 RL

From: Bijan Parsia <bparsia@cs.man.ac.uk>
Date: Fri, 23 Jan 2009 10:30:56 +0000
Message-Id: <45BEE397-16C6-4DE0-B7D3-82D609A964A2@cs.man.ac.uk>
Cc: Boris Motik <boris.motik@comlab.ox.ac.uk>, 'W3C OWL Working Group' <public-owl-wg@w3.org>
To: Ivan Herman <ivan@w3.org>

On 23 Jan 2009, at 08:51, Ivan Herman wrote:

> Boris,
>
> before we do this... let me just raise this issue: just because we  
> _can_
> does not meant that we necessarily _should_.
>
> In my view, one of the goals of RL is a possibility for an easy
> implementation, too.

All of the profiles have the possibility of an easy implementation.  
For some value of "easy".

> With my limited implementation experience the
> datatype handling of RL is by far the most complex part of an
> implementation.

I wouldn't be too surprised but it partially depends on the existing  
capabilities of the language, libraries, or system you're using. For  
example, if you  had to implement a rule engine as well I sincerely  
doubt OWL RL (without datatypes) would be considered "easy", esp. in  
comparison with EL++.

> Sure, if one goes for a very efficient implementation
> then taking care of things like owl:sameAs becomes also more complex,
> but that is not 100% necessary for a compliant thing.

It's unclear to me why we should optimize the language for the easy  
to implement/naive implementation case, esp. wrt compliance.

> Datatype handling
> is. (I actually did not even have the time to implement it, I just  
> rely
> on the underlying RDF/Python environment and do whatever it can do. I
> can see many implementations doing just that.) Oracle has already
> indicated that they are not really in favour of an owl:rational
> inclusion in OWL RL, and I think their reaction reflects the same  
> concerns.

This is a very different, IMHO, consideration, because Oracle *is*  
talking about a production quality system.

> Based on this I actually do _not_ believe that this is just an  
> editorial
>  comment but would definitely warrant a new LC round because it would
> significantly add to the complexity of implementations.

It's unclear to me since it's unclear that the marginal extra effort  
in production systems is so bad as to warrant the interop gap. As Jos  
points out, it's just range testing of a concrete literal. This is  
pretty straightforward.

> My personal
> interpretation (maybe wrong!) of that comment in the document is that
> some datatypes (like rational) may actually be dropped from the  
> list and
> not add all other datatypes blindly...

"""Feature At Risk #2: OWL 2 RL Datatypes
The list of normative datatypes in OWL 2 RL may be reduced based on  
feedback."""

Alas, seems straightforward. I'd have preferred "changed" since this  
is unnecessarily restrictive.

Cheers,
Bijan.
Received on Friday, 23 January 2009 10:27:41 GMT

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