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: Tue, 28 Jun 2005 15:17:33 -0400
To: Ian Horrocks <horrocks@cs.man.ac.uk>
Cc: Bijan Parsia <bparsia@isr.umd.edu>, Jim Hendler <hendler@cs.umd.edu>, www-rdf-rules@w3.org, dreer@fh-furtwangen.de, Jos de Bruijn <jos.debruijn@deri.org>
Message-Id: <20050628191733.A9649CB5D3@kiferserv.kiferhome.com>


Ian,

The difference is really between SWRL and everything else, and SWRL should
be developed by a different WG, if there is a need for a rules language
sitting on top of OWL.

N3 is essentially a different syntax for F-logic and its extensions (but
N3's semantics is defined by use cases ;-). As far as I can tell, with each
new presentation that I hear N3 is moving in the direction of LP.


	--michael  


Ian Horrocks wrote:
>
> On 23 Jun 2005, at 05:54, Michael Kifer wrote:
> 
> >
> >
> > Jim,
> > So, you are saying that LP is at the same stage as DAML+OIL before
> > standardization. What is needed is to work out the details --  
> > typically a
> > job for a working group.  Who disagrees with that?
> 
> I do not agree that the current situation w.r.t. "rules languages" is  
> comparable to the one appertaining w.r.t. "ontology languages" when the  
> WebOnt working group was chartered. At that time there was a single  
> candidate ontology language around which a broad consensus had already  
> been built (e.g., through the merging of the OIL and DAML-Ont efforts).  
> Currently there are several competing rules language proposals, with no  
> obvious (to me) leading contender.
> 
> I also disagree with the suggestion that a Working Group is likely to  
> be able to resolve major technical problems - if you look at what went  
> in to WebOnt (DAML+OIL) and what came out (OWL), you will see that they  
> are relatively similar. This is not to minimise the quality or quantity  
> of the work carried out within WebOnt - it simply illustrates how  
> difficult it is to get a large and heterogeneous WG to agree on  
> anything, never mind agreeing on significant technical changes, and how  
> much effort is required to go from a prototype to a finished product.
> 
> So, your argument leads me to the conclusion that either (a) one of the  
> candidates should be (arbitrarily?) chosen for standardisation, (b) a  
> WG should be established without any clear indication as to what should  
> be standardised, or (c) several WG's should be established - one for  
> LP, one SWRL, one for N3, etc. Option (a) is hardly likely to promote  
> consensus building, option (b) seems to be a recipe for years of  
> unproductive argument, and option (c) would be very costly (for both  
> the W3C and the semantic web community), and very confusing for those  
> considering the adoption of semantic web technology.
> 
> A fourth alternative, and one that I think several people in this  
> thread have been arguing for, is to continue working (in whatever  
> context) towards an architectural framework that provides for a better  
> integration between First Order and LP based languages. We should then  
> be able to achieve the broad consensus which is, I believe, a necessary  
> (or at least highly desirable) precursor to the initiation of a  
> standardisation activity.
> 
> Regards,
> 
> Ian
> 
> 
> 
> 
> >
> > And you didn't need to defend OWL because nobody was attacking it.  Our
> > discussion was about the 1-stack vs. multi-stack architectures. Since  
> > in a
> > previous email you said that you are "not against a multi-stack  
> > solution"
> > then I don't see what is the point of contention (at least at the high
> > level). I believe that everybody agrees that the more integration --  
> > the
> > better. We just don't believe that integration of the leading useful
> > technologies to the point that only one stack is left is possible.
> >
> >
> > 	--michael
> >
> >
> >> Mike - I think you're missing the point of the "webbie" nature of OWL
> >> and the difference from traditional KR, but I have written that up
> >> too many times to do it again here.  With LP, the question is how I
> >> can use your rules/program/etc. in part to get a "network effect" and
> >> to make it so I can link together the logics and logic programs as
> >> easily as I link web pages.  It;s not that no one has good research
> >> ideas on how to do that, it's how to bring those to fruition and
> >> greater use that is the key
> >>     The ontology stuff in OWL, which is not actually DL (even  OWL DL
> >> departs from traditional DL in some interesting ways, but OWL Full is
> >> the one I care most about) is based on many years of work in AI, and
> >> was explored on the web long before OWL was done - cf the SHOE work
> >> my group did (still a high hit at Google - so just google "shoe") and
> >> that was followed by XOL, OIL, and others before the standardization
> >> began.
> >>   I think the LP stuff is in similar state - a basic idea has been
> >> fleshed out, some variants are being explored, and there is a govt
> >> interest in pushing for a de facto standard.   But  going from there
> >> to the finish line is where a lot of the time and blood goes in --
> >> it's in making the stuff fit with what else is out there in the Web.
> >> We had to do a lot of work to make OWL fit in with RDF and other
> >> languages it needed to interoperate with, and a web rules language
> >> needs to be defined with the other things already in the space it
> >> wants to play in (thus the "stacks" issue - if it wants to be in a
> >> Sem Web stack, it needs to play with other SW stuff; if it wants to
> >> be in the XML stack, it needs to play nice with XML stuff like Xquery
> >> and Xpath, etc.
> >>   And that is the discussion we are having -- but if we can nail this
> >> stuff, the result is worth it -- OWL is certainly the most used
> >> KR/ontology langauge in the history of AI as best anyone can tell,
> >> and if we want the Web Rules Language to flourish we want it to grow
> >> like the Web does, not like rules languages have -- nothing wrong
> >> with the latter, but there's a whole lot more Web pages out there
> >> than logic programs, and it's a lot more fun to play in the
> >> exponential growth space :-)
> >>   anyway, we're all working for same ends, just different means, and
> >> finding the consensus space in the middle is wondefully non-fun, but
> >> worth it in the end
> >>
> >>   Ok, end of crap, back to technical issues and Greek symbols...
> >>   JH
> >> p.s. please note - I spent many years of my career arguing against DL
> >> and doing scruffy AI - yet here I am defending OWL - why?  because
> >> the design time and fights over the details of a number of use cases
> >> ended up creating something pretty damn useful -- both in the OWL DL
> >> space and in the OWL Full space -- so somehow the process worked...
> >>
> >>
> >> At 20:41 -0400 6/22/05, Michael Kifer wrote:
> >>> Jim Hendler wrote:
> >>>>
> >>>>  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.*
> >>>
> >>> I think it is not just me, but a number of people who read your  
> >>> paper on
> >>> the two stacks may have misunderstood it. At least one way to  
> >>> understand
> >>> what is said there is that 1 stack is good and 2 is not.
> >>> If there is another way to understand it (as advocating a multi-stack
> >>> architecture) then this second meaning is deeper than I was able to  
> >>> dig up.
> >>>
> >>>>    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)
> >>>
> >>> You didn't say this and I didn't say that you said this.  I was
> >>> focusing on what I think were technically inaccurate claims in your  
> >>> email
> >>> regarding the layering of WRL on top of DLP (where WRL is taken to  
> >>> mean the
> >>> particular language under this name and not "a" generic 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])
> >>>
> >>> Not "applying LP in the Web area" but "adapting LP to the Web".
> >>> Technically, OWL is an adaptation of DL to the Web with some  
> >>> additional
> >>> research needed to accommodate RDFS.  But in the LP area this  
> >>> research has
> >>> already been done years ago.
> >>>
> >>>>  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.
> >>>
> >>> Of course URIs are crucial. After all, they are object identifiers,  
> >>> so they
> >>> are as crucial as any notion of an Id.
> >>>
> >>> But do they imply/require a new kind of KR?  There are interesting  
> >>> new
> >>> problems that stem from the architecture, but don't make it sound as  
> >>> if the
> >>> "old KR" is out of the window and adapting it to the new  
> >>> architecture is a
> >>> hard or pointless exercise. The LP paradigm is as applicable to the  
> >>> Web as
> >>> DL, if not more. (I, of course, think that it is more :-)
> >>>
> >>>
> >>>>    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
> >>>
> >>> The term "rules" is ambiguous in the context of our discussion. If  
> >>> you said
> >>> "I don't see this as in any way being a discussion of *LP* vs.  
> >>> ontology"
> >>> then this is exactly what I was trying to say. As I remarked above,
> >>> the 2tower paper **appears** to be arguing that LP+OWL in a 2-stack
> >>> architecture is a nonstarter.
> >>>
> >>>
> >>> 	--michael
> >>>
> >>>
> >>>>    -JH
> >>>>
> >>>>
> >>>>  [1] http://www.w3.org/2003/08/owlfaq.html
> >>>>  [2]
> >>>>
> >>>> http://www.sciam.com/article.cfm?articleID=00048144-10D2-1C70 
> >>>> -84A9809EC588EF21
> >>
> >> -- 
> >> 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 Tuesday, 28 June 2005 19:17:58 GMT

This archive was generated by hypermail 2.2.0+W3C-0.50 : Monday, 7 December 2009 10:53:12 GMT