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Re: Web Rule Language - WRL vs SWRL

From: Jim Hendler <hendler@cs.umd.edu>
Date: Wed, 22 Jun 2005 18:03:28 -0400
Message-Id: <p0620078bbedf8cc6996e@[]>
To: Michael Kifer <kifer@cs.sunysb.edu>, Bijan Parsia <bparsia@isr.umd.edu>
Cc: www-rdf-rules@w3.org, dreer@fh-furtwangen.de, Jos de Bruijn <jos.debruijn@deri.org>
Mike - I think you misunderstand the stuff about stacks and etc -- I 
hope my use cases (in public-sws-ig@w3.org for those just joining the 
conversation) would help make it clear that these are not separate 
and unrelated stacks, nor are they identical things -- the key is 
figuring out how the stacking works and how things interact -- I'm 
not against a "multi-stack: solution, but as far as I am concerned 
the more overlap the better, and I am fairly sure that we can do 
significantly better than DLP in terms of providing a useful web 
rules language that interacts well with the existing, and becoming 
more widely used, ontology spec.*
  Seems to me the key is exploring how to get maximum interoperability 
between the important work in BOTH areas (and I defy you to go back 
through this discussion and find any email where I haven't said I'm 
in favor of a web rules language) and also how to get the Web rules 
to join in the growing whole that is the semantic web -- it's not the 
same as applying LP in the Web area -- I argued for nearly a decade 
about the difference between Web Ontology and standard AI KR 
languages, and OWL has some significant differences from traditional 
AI (see the OWL FAQ [1] and the discussion of KR  back in the 2001 
Scientific American article [2])  This latter, btw, explains why URIs 
are not just some wildassed thing, they're crucial to the Semantic 
Web in a very deep way - read the Sci Am or any of Tim's discussions 
of this issue.

  so, I don't see this as in any way being a discussion of rules vs. 
ontology -- in fact, I cannot think of any dumber way to approach it 
-- rather it seems to me we're trying to explore where these things 
can overlap to the benefit of users and of the Web -- that strikes me 
as a very worthwhile pursuit

[1] http://www.w3.org/2003/08/owlfaq.html

  * If you want to argue the rules language somehow replaces the 
ontology stack, I'll ask you to show how many large ontologies in 
areas like Life Sciences and Digital Libraries have been built in 
Prolog or other LP langauges... but the answer appears to be 
vanishingly close to zero, now compare that with GO, OBO, NCI 
ontology, and the growing number being expressed in OWL - the OWL 
spec is quite healthy, and doing well, I can't imagine anyone would 
argue for getting rid of it unless they are some AI purist who has no 
clue of what the Semantic Web vision is about -- oops, I risk going 
personal and ad hominen, so I'll stop here]

At 15:49 -0400 6/22/05, Michael Kifer wrote:
>Bijan Parsia wrote:
>>  Perhaps this should move to rdf-rules?
>>  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.
>>  >    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
>>  > 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

Professor James Hendler			  Director
Joint Institute for Knowledge Discovery	 	  301-405-2696
UMIACS, Univ of Maryland			  301-314-9734 (Fax)
College Park, MD 20742			  http://www.cs.umd.edu/users/hendler
Received on Wednesday, 22 June 2005 22:05:43 GMT

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