Re: Web Rule Language - WRL vs SWRL

Bijan Parsia wrote:
>
> Perhaps this should move to rdf-rules?

Perhaps.


> On Jun 22, 2005, at 11:29 AM, Michael Kifer wrote:
> 
> > Bijan Parsia wrote:
> [snip]
> >> To extend the conversation in another direction, is there any reason 
> >> to think
> >> that a logic programming paradigm, in general, is the right approach 
> >> to nonmon
> >> on the Web? Representationally? There are many non-monontonic 
> >> formalisms
> >> (consider default logic and autoepistemic logic) and it might be that 
> >> they 1) are
> >> better for web contexts and 2) play better with owl. (It's plausible, 
> >> for example,
> >> to think that default logic can be made to fit better because of the 
> >> separatation
> >> of the base representation and the default rules. Even there, 
> >> adjustements must
> >> be made.)
> >>
> >> (Of course, anything in this space runs into the problem that, in 
> >> general,
> >> nonmon formalism are much more computationally difficult than 
> >> corresponding
> >> monotonic ones. The LP position often appeals to the 
> >> scalablility/computational
> >> goodness of, say, deductive databases. But if that comes at the price 
> >> of
> >> throttling back expressivity forever...maybe it's not such a great 
> >> idea. Pat Hayes
> >> often, to my understand this, as thinking of nonmon constructs as 
> >> part of the
> >> *data* on the web (to his mind, bad), and nonmon as a way of 
> >> *reasoning with*
> >> the data on the web (good...it's located in the agent or processor 
> >> which is in a
> >> position to make certain assumptions with a good sense of the risks)).
> >
> > These are all valid points for future research.
> 
> That's the extension of the conversation I'm after.


I think it is a research program. I don't think much, if anything, can be
accomplished on a mailing list.


> > I believe, however, that
> >
> > 1. It is naive to assume that one single formalism like DL or LP would
> >    serve the humankind forever.
> 
> I certainly don't think that.

Good!


> >    The architecture should provide for multiple formalisms (where the
> >    formalism would be identified together with the statements -- RuleML
> >    attempts to do something like that).  The communicating parties will
> >    either be able to talk (if they both understand that particular 
> > formalism)
> >    or they won't, but at least they will know it.
> >    Certain degree of interoperability between the different formalisms 
> > can
> >    be provided without them being built on top of each other.
> 
> This is going in a different direction, which I'm sympathetic too. But 
> it seems to end up in the land of multiagent systems (with agents 
> wrapping and mediating different data sources). That *doesn't* seem 
> like the semantic web as I've heard it articulated.
> 
> Maybe the semantic web as such is impossible!


I don't know what "semantic web as such" is, but I do believe that
defining it as a single stack is doomed to fail.


> > 2. Regarding the suitability of LP, this is backed by over 30 years of
> >    practice.
> 
> Hmm. Yes and no, right? The question is suitability *for what*. Of 
> course, we're all groping in the dark, really.

LP has been used for knowledge-intensive apps for as long as I stated.
Webby things are not that different -- just another application.  There are
interesting problems for sure, but it is funny to watch some of the
discussions in which people create fetishes and pray to the god of URLs.

> The W3C made a bet 
> though that is not easily reconcilable with LP (and components of 
> which, at least, have similar depth in background). So, do we zig? Zag? 
> Stay the course? Stay mostly the course? Start over?

So, they erected one stack - this is fine. If they will insist that this is
the one and only true stack, then the thing is going to die due to
irrelevance.


> > Default logic is nice, but it is just a theoretical tool at
> >    this point. Before it (or its derivatives) can make into a Web 
> > standard,
> >    I suggest to give it a try (or **practical** use) for, say, 10 
> > years by a
> >    reasonably sized user community.
> 
> While that would be my general suggestion for *EVERYTHING* :), betting 
> seems to be the name of the game.

See, organizations like OASIS let their standards to die. If W3C is fine
with that then they can bet all they want.
But it seems to me that W3C is not prepared to kill its own standards, and
in this case it should bet very carefully and with an eye on the future.

> 
> Looking at LP land, I don't see systems doing the "Web" thing. Of 
> course, I'm not entirely sure what the web thing *is* really. I'd love 
> to have better clarity on that so we could figure out what really 
> *should* be going on.

Exactly. What is the "Web" thing precisely?
If you view it as a large distributed KB then LP is arguably doing this.


> However, and I think it's a reasonable position, you are actually 
> advocated a non-integration strategy. (As you said in one.) That's 
> fine, but then I would like it if those cards were laid on the table 
> instead of claims of integration, overlap, compatibility (let me note 
> that you are not the one making such claims). Let's change the freaking 
> architecture to a hub and spoke, or whatever.

As I said, it is presumptuous to claim that the current technology will
remain true for all times -- even for 5 years from now.  A realistic
architecture should allow for more spokes.

> Why two stacks instead of 
> twenty and how do you make those twenty talk *at all*?

One way for them to talk is to allow them to view each other as black boxes
and send queries to each other. This is essentially the architecture of
AL-Log. The Eiter et all. papers that you cite in your paper take the same
approach and try to integrate DL with LP a bit tighter.

It is strange that you even cite Eiter's paper because, if anything, this
paper is an argument that a single stack is a bad idea and that several,
loosely integrated, stacks is a way to go.


> This is close to the RuleML view of things. I've watched RuleML for 
> quite a while and I still believe that its approach, while appeal, is 
> not the kind of thing that the W3C likes to do. They like to pick 
> winners, rather than pick integration formats. (Of course, they like 
> picking winners at the "right" level...XML is pitched, after all, as an 
> integration format!)

Winners? How do they determine who the winner is? (The rest of the diatribe
is not for a public list :-)


	--michael

Received on Wednesday, 22 June 2005 19:51:21 UTC