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 16:49:06 -0400
To: bparsia@isr.umd.edu
Cc: www-rdf-rules@w3.org
Message-Id: <20050629204908.36DAE19E75F@kiferdesk.lmc.cs.sunysb.edu>

Bijan Parsia wrote:
> >> [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.

It has been clear to those who claimed it.
You might have had a different set of defaults though.

> 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 
> interoperabilty.

You may be exaggerating the "plenty" and the "great deal" parts.

> 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.

No, nothing is free (except for an occasional lunch).

> Which, I would submit, is a reasonable objective.

Some objectives might be reasonable, but unachievable.

> Anyway, whatever.
> [snip]
> >> (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.

This reminds me of the early days of SQL. Back then people believed that
practitioners will actually understand the semantics *and use it*.
The reason SQL is  such a screwed-up language is because the authors went
out of their way to make it "understandable" by non-experts.
(Back then people thought that a company manager will actually be able to
type correct queries and get answers from a DBMS.)

Even the much more user-friendly languages like QBE and its derivatives
(like MS Access) have some hairy semantic problems. But they get the 80% right.

> [snip]
> >> (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" :)

Yes. Otherwise I would have to debate with you what "enough" means.


> >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.

It depends how high is your sky. If you are aiming at the 7 heavens, then
it is perhaps too high.

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

Yes, why?

> 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.

I don't believe that arbitrary is possible. But reuse of solutions is possible.


> (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.)
> Cheers,
> Bijan Parsia.
Received on Wednesday, 29 June 2005 20:49:14 UTC

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