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Re: draft public comment for OWL last call from RIF

From: Bijan Parsia <bparsia@cs.man.ac.uk>
Date: Fri, 23 Jan 2009 15:15:07 +0000
Message-Id: <55A8AB42-13CF-4F9F-ACEB-318DF7B4A89B@cs.man.ac.uk>
Cc: Bijan Parsia <bparsia@cs.manchester.ac.uk>, Sandro Hawke <sandro@w3.org>, Dave Reynolds <der@hplb.hpl.hp.com>, "Public-Rif-Wg (E-mail)" <public-rif-wg@w3.org>
To: Chris Welty <cawelty@gmail.com>

On 23 Jan 2009, at 14:20, Chris Welty wrote:

> Bijan,
>
> While RIF and OWL are clearly different, and have different goals,  
> they are also very similar, and there is a significant portion of  
> the world that views them that way.

That's fine. All I'm arguing is that it's not *ridiculous* (your  
term!) for there to be divergence in the *set* of datatypes supported.
<http://www.w3.org/mid/4978939C.3000900@gmail.com>
	"""Stepping back from RIF and OWL, it seems ridiculous to me that  
each would maintain a different set."""

"Ridiculous" means there's no case to be made. I believe there is a  
case to be made (depending on the circumstances). There's also a case  
to be made against.

One could make a better case that difference in the *semantics* of  
same named datatypes should be the same. But even there, OWL does  
*different things* with the datatypes (i.e., it treats them as  
constraints).

> (Recently, giving a RIF talk, I was asked "So which do I use, OWL  
> or RIF?"  I did not perceive from the rest of the audience any  
> indication that this seemed a ridiculous question.)

I don't see that it's a ridiculous question even if the datatypes  
diverge. One possible answer would be "OWL supports owl:rational, so  
if you need that, either work with OWL or an extension of RIF."

I don't see that that's a ridiculous answer.

> So while you see no strong argument to have the same set of  
> datatypes, I see no strong argument *not* to make them the same,

The strong argument is that the OWL community wants, afaict, more  
datatypes than, from what you seem to indicate, RIF implementors want  
to support. Since I'll bet that *all* systems that will use RIF for  
interchange that are outside RIF, I don't see why OWL has to be held  
to the lowest common denominator.

> quite the opposite in fact - it seems plainly obvious to me they  
> should be the same.

"Plainly obvious" is not an argument of *any* kind.

> You have given no strong argument here, other than your own  
> personal motivations.

How are my "personal" motivations as a prominent vendor and users of  
OWL systems irrelevant? It's certainly more relevant than bare  
assertions otherwise.

If you like, I hereby say that the University of Manchester has an  
interest in a expansive set of datatypes to be supported in OWL  
including owl:rational. See the *extensive* discussion about it in  
the OWL archives.

> And I do not think it futile

I think it's futile because I think, and plan, to add a number of  
additional datatypes to OWL For example:
	http://www.webont.org/owled/2008/papers/owled2008eu_submission_44.pdf
which has a lot of support (including from the Product Modeling XG).

I suspect that some RIF based vendors' user bases do not need such  
types, thus I'd be surprised if they would get into the "common  
denominator" of RIF. But there's no reason, therefore, for them  not  
to be in the common denominator of (a future) OWL.

Interchange between widely disparate systems often is well served by  
restrictions. User modeling often is not. Hence, the futility.

> - if you believe its non-futile

I don't believe it is non-futile. Or, more to the point, I don't  
think it's necessary. Without *some* argument for why they being the  
same (esp. as extant SW languages such as RDF and OWL 1 haven't had  
the same set) is an overriding consideration, I don't feel any extra  
burden of proof at all. I have plenty of arguments for the datatypes  
Manchester wants. I don't presume to tell RIF vendors what datatypes  
their users want so accept their arguments that they want fewer  
datatypes. Thus, we have a divergence. If all other things were  
equal, I'd happily synchronize them, but the burden of proof is that  
all other things are equal. You are trying to shift the dialectic  
such that divergence is not just prima facie wrong, but requires  
heroic arguments to overcome. I don't see that that's a shared  
presumption. I don't share it. OWL 1 and RDF WGs didn't share it.

> and should be the job of one working group to formally designate a  
> set of datatypes, then it is certainly possible for two working  
> group to do it, albeit the amount of work increases by an order of  
> magnitude which I don't relish.  None the less, I see this as our  
> responsibility.

I'm happy with having divergent sets of datatypes *within OWL  
Profiles* though I do prefer, all things being equal, for them to be  
the same. But I'm happy to consider, without prejudice,  
implementation and user base considerations.

> We do seem to agree that the set of datatypes should have the same  
> semantics.

Up to a certain point, yes. E.g, I wouldn't want to force RIF  
implementations to do CLP by default.

> This makes me think I should send two message from RIF, one on the  
> different semantics and one on the common set of datatypes.

I would recommend that. I would also recommend that you don't presume  
that everyone agrees with what you find obvious or is ridiculous.

When it comes down to it, as a user, I don't care about owl:rational  
in RIF, but I really care about it in OWL. That's why I didn't make  
an LC comment to RIF about the lack of owl:rational.

Cheers,
Bijan.
Received on Friday, 23 January 2009 15:11:48 GMT

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