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Re: Web Rule Language - WRL vs SWRL

From: Bijan Parsia <bparsia@isr.umd.edu>
Date: Wed, 29 Jun 2005 00:58:58 -0400 (EDT)
To: Michael Kifer <kifer@cs.sunysb.edu>
Cc: www-rdf-rules@w3.org
Message-Id: <20050629005858.CRH00973@isrmail.isr.umd.edu>

---- Original message ----
>Date: Wed, 29 Jun 2005 00:23:53 -0400
>From: Michael Kifer <kifer@cs.sunysb.edu>  
>Subject: Re: Web Rule Language - WRL vs SWRL   
>To: Bijan Parsia <bparsia@isr.umd.edu>
>Cc: www-rdf-rules@w3.org
>> [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.

Perhaps you should just acknowledge that most of the pro-DLP patter has been 
very *unclear* about exactly what compatibility it affords.

I mean, you claim that the claimed interoperabilty was limited in certain ways 
but 1) I've not heard that *limited* claim from the DLPers before this and 2) I've 
heard plenty that, I'll, for the sake of charity, say "suggests" a great deal of 

Even if they are, up to "pragmatically negligable" semantic mismatch, 
semantically compatible, the subsetting approach doesn't actually allow for 
reasonably free interaction between the formalisms. Which, I would submit, is a 
reasonable objective.

Anyway, whatever.

>> (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.

No need to make them moreso.

>You seem to think that practitioners delve into the semantics of things --
>big mistake! 

The practictioners I work with do. I encourage and support them in that.

>> (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. 

You did get that you were in the scope of the "no one" :)

>> 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 :-)

So we hope.

>> 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.

Wow...good thing I didn't say that. I *hate* to be an  optimist, even more so an 
incurable one.

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

And on the Web, we will expect a kind of interoperability between solutions to 
these problems and a *chance* of reusing your solution to a particular problem 
in a context that you did not imagine.

Or rather, I think that's what we're aiming at, pie-in-the-sky as it may be.

So, why don't we talk about possible integration frameworks?

After all, if we can put a plausible solution on the ground I think we can move 
forward. And, if we are to follow what you've said thrice, it should be a 
framework that supports arbitrary KR integration.

(RuleML is, of course, a good case study or cautionary tale. It is tackling things 
head on, yet seems rather unsatisfactory (perhaps it's just the syntax ;)). Or, at 
least, not getting people engaged with the integration vibe.)

Bijan Parsia.
Received on Wednesday, 29 June 2005 04:59:13 UTC

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