Re: Web Rule Language - WRL vs SWRL

Bijan Parsia wrote:
>
> ---- Original message ----
> >Date: Wed, 22 Jun 2005 10:46:36 -0400
> >From: Jim Hendler <hendler@cs.umd.edu>  
> >Subject: Re: Web Rule Language - WRL vs SWRL  
> >To: Jos de Bruijn <jos.debruijn@deri.org>, dreer@fh-furtwangen.de
> >Cc: public-sws-ig@w3.org
> [snip]
> >Sorry, but this cannot be right.  SWRL assumes closed world semantics 
> >and WRL assumes open world semantics.   
> 
> Thinko/typo on Jim's part. It's the other way around of course.
> 
> > Thus, we get completely 
> >different entailments in an OWL/RDF world than in a WRL one, so we 
> >are talking something very different than a subset relationship.  Ian 
> >Horrocks, Peter Patel-Schneider, and Bijan Parsia (with me as a 
> >kibbitzer) wrote a short paper about this available at [1]
> >
> >Let me be clear, I'm all for Web (and Sem Web) rules languages, but 
> >if it isn't open-world, I don't see how it can be Sem Web, since it 
> >violates the base assumption on which all of RDF, RDFS, and OWL sit. 
> >This is easily fixable, and at the Rules workshop the idea of a 
> >"Scoped Negation as Failure" was developed to handle this -- I'd love 
> >to see WRL (and SWRL) extended to have a SNAF mechanism, because then 
> >we don't violate the basic principles of the Web architecture and the 
> >Semantic Web, but we should be precise - two things with very 
> >different Semantics and entailments cannot be referred to as subsets 
> >of each other.
> [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.
I believe, however, that

1. It is naive to assume that one single formalism like DL or LP would
   serve the humankind forever.
   
   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.

2. Regarding the suitability of LP, this is backed by over 30 years of
   practice. 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.


	--michael

Received on Wednesday, 22 June 2005 15:29:19 UTC