W3C home > Mailing lists > Public > www-rdf-rules@w3.org > June 2005

Re: Web Rule Language - WRL vs SWRL

From: Michael Kifer <kifer@cs.sunysb.edu>
Date: Wed, 29 Jun 2005 00:23:53 -0400
To: Bijan Parsia <bparsia@isr.umd.edu>
Cc: www-rdf-rules@w3.org
Message-Id: <20050629042353.93130CB5D3@kiferserv.kiferhome.com>


> [Trimming down to www-rdf-rules]
> On Jun 28, 2005, at 3:09 PM, Michael Kifer wrote:
> [snip]
> 
> > This wasn't clear from the paper.
> > In any case, the claimed interoperability doesn't extend to the more
> > powerful languages.
> 
> That this wasn't claimed (or at least strongly suggested) certainly 
> isn't clear from the architecture diagram that has rules and OWL 
> "overlapping" with DLP. Similarly, the DLP "shield" diagram also 
> strongly suggests that the interoperabilty isn't restricted in the way 
> you suggest.


Sorry, you lost me here...
In any case, I see no point in arguing about what was "suggested" or
"clear" from this or that diagram.


> > Your argument is well-taken. However, if you are querying an ontology 
> > with
> > an LP language then you expect that CWA will be applied in the current
> > state.
> 
> Er... I do? Really? Bit odd for a black box integration approach, I 
> think.
> 
> (If my query contains an explicit default negation operator, this is 
> closer, although (given non-distinguished variables) certain 
> (non-ground) things may be provable on one semantics and not the other, 
> so the results might still differ. Also, cardinality/counting queries 
> may (or may not!) have implicit default negation, but my expectations 
> (having worked with OWL for a while) will, well, be toward an open 
> world. Given that OWL will have been around (and pushed) by the W3C for 
> several years before a Rules wg can produce a recommendation...things 
> could get confusing.


Things are already confusing and they aren't likely to become clearer.
You seem to think that practitioners delve into the semantics of things --
big mistake! 


> [snip]
> 
> > There will be certain amount of semantic mismatch, but this most likely
> > won't matter. From talking to people I get the impression that
> > they build very simple ontologies using OWL. Most of them are in DLP 
> > with
> > some use of cardinality restrictions. However, when I press, it turns 
> > out that
> > people don't understand what cardinality restrictions mean in OWL. They
> > think they are like cardinality constraints in databases.
> 
> I was just reminded how similar assertions based on "taking to people" 
> led to the removal of qualified cardinality restrictions in OWL. That 
> turned out to be a big mistake.
> 
> (All I mean is that while I have some similar experiences, I don't have 
> *enough* experience (and think no one does) in building web KR to have 
> a good idea what people *should* want!

Yes, it is a common problem. 

> I know you think that Web KR is 
> not a big thing or substantively different from regular KR, but I'm not 
> convinced.


Web KR is KR for the masses :-)


> There are aggregation and integration support arguments from both sides 
> of the divide. Anyhoo.)
> 
> > People think databases but use OWL.
> > Now, this is a real semantic mismatch: people mean (and want!) one 
> > thing,
> > but get a completely different thing.
> [snip]
> 
> How is this different than arguing that OWL should be largely abandoned 
> (for the SemWeb, in general)? If this is the conclusion, let's bring it 
> out.
> 
> (Obviously, a decent dialectical move on your part would be to say that 
> OWL won't be able to face the competition, if it's on even ground, or, 
> if it could, then proponents wouldn't try to argue against adding the 
> competition except perhaps from beneficent, paternalistic "don't waste 
> your time" grounds. Of course, a reply would be to point out that the 
> choice won't seem so clear and so there's the possibility of damaging 
> all houses with no gain.)


I said this twice in previous emails, but let me say it again in a
different form. Someone who believes that there is one solution to all KR
problems on the Web is an incurable optimist in view of the history of
programming languages and KR.

That is, there are problems that are best solved with FOL (incl. OWL) and
there are problems for which LP is best.


> (Er..I could go on arguing with myself, but I don't want to have to 
> auto-insult ;))
> 
> Cheers,
> Bijan Parsia.
> 
> 
Received on Wednesday, 29 June 2005 04:24:02 GMT

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